Legal glossary

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51% attack

An attack in which a single entity controls more than half of the network's mining power, enabling it to exclude transactions or reverse its own recent ones. It does not allow the attacker to spend coins it does not control or to change the protocol rules.

A

A contrario

An argument that because a rule names a category, it does not apply outside it. The opposite of reasoning by analogy. Assumes silence means deliberate exclusion, which is not always true.

A fortiori

An argument that if a rule applies to a weaker case, it applies with greater force to a stronger one.

A posteriori review

Constitutional review of a law after it has entered into force.

A priori review

Constitutional review of a law before it enters into force, typically on referral by defined officials.

Ab initio

From the beginning. An act void ab initio never had any legal effect at all, as opposed to one that ceases to have effect from some later moment.

Abuse of power

Using a power granted for one purpose to achieve another. A ground for annulling an administrative decision, usually proved by inference from the sequence of events rather than by admission.

Abuse of right

Exercising a right you genuinely hold, but for no purpose other than to harm someone, or in a way grossly disproportionate to any benefit. Prohibited in most civil law systems.

Acquisitive prescription

Acquiring ownership through prolonged possession in defined conditions: typically peaceful, public, continuous and as owner. Aligns legal title with long-settled facts. The common law counterpart is adverse possession, which works on a similar principle with different requirements.

Act

Two meanings. A statute passed by a legislature. Or, in civil law usage, any manifestation of will producing legal effects. See legal act.

Address reuse

Using the same Bitcoin address for more than one transaction. It exposes the full history of that address publicly and allows third parties to link payments together. Standard practice is a fresh address for each payment.

Adjudication

A court or tribunal deciding a dispute authoritatively.

Administrative act

A decision by a public authority. May be general, applying to a class, or individual, applying to a named person.

Administrative law

The branch of public law governing public authorities: their powers, the limits on them, and remedies against them. In practice the branch citizens encounter most.

Administrative sanction

A penalty imposed by a public authority rather than a court: a fine, licence suspension, exclusion from a market. Procedurally lighter than criminal proceedings, which is why their use has grown.

Admissibility

Two meanings. Whether a claim may be heard at all, given standing, time limits and form. Or whether a piece of evidence may be used.

Adversarial system

A procedural model in which the parties gather evidence and drive the case while the judge umpires. Traditionally associated with common law systems, though the contrast is a pedagogical shorthand rather than an accurate modern description: civil law proceedings can be strongly adversarial, and common law courts exercise substantial case management. Contrast inquisitorial.

Agency

Two meanings. A public body with regulatory functions. Or, in private law, the relationship by which one person acts on another's behalf and binds them.

Amicus curiae

Literally friend of the court. A third party permitted to submit observations in a case it is not a party to, usually because it has expertise or a broader interest in the outcome.

Analogy

Reasoning that a case resembling a decided one in the respects the rule cares about should be treated the same way. In systems recognising the principle of legality, reasoning by analogy to extend criminal liability to the defendant's detriment is generally prohibited, since offences must be defined in advance. Reasoning favourable to the accused is treated differently in many systems.

Annex

A schedule attached to an instrument containing technical detail, lists, thresholds or forms. Frequently where the operative substance actually lives.

Annulment

A remedy treating a decision or instrument as never having existed. The characteristic remedy of administrative law.

Appeal

Review of a decision by a higher court. Depending on the system and level, may cover facts and law or law only.

Arbitration

Private dispute resolution by a tribunal the parties chose, producing a binding award. Dominant in international commerce because awards are comparatively easy to enforce across borders.

ASIC

Application-specific integrated circuit. Hardware designed solely for Bitcoin mining, far more efficient at that one task than general-purpose computers.

Assignment

Transferring a right, typically a claim, to another person. Often requires notice to the debtor to be effective against them.

Asymmetric cryptography

A cryptographic system using a pair of keys: a public key that can be shared openly and a private key kept secret. What one key does, only the other can undo. This is the foundation of Bitcoin ownership.

Audi alteram partem

Hear the other side. The principle that no adverse decision should be taken without giving the affected person a genuine opportunity to respond.

Autonomous regulation

Executive rule-making power held directly under the constitution, requiring no enabling statute. Exists in some systems for matters outside the legislature's reserved domain.

Award

The decision of an arbitral tribunal. Binding on the parties and enforceable much like a judgment.

B

Bare ownership

Civil law concept: ownership stripped of use and fruits, which are held by a usufructuary. Full ownership reunites when the usufruct ends. Common law reaches comparable outcomes through trusts and life interests.

Basic norm

Kelsen's presupposed foundational norm at the summit of a legal order, grounding the validity of the constitution. Not itself enacted; presupposed rather than proved.

Beneficial owner

The person who ultimately owns or controls an asset or entity, as opposed to whoever appears on the register. Central to anti-money-laundering regulation.

Bicameral

A legislature with two chambers, both of which must normally approve a text. Deliberately slows legislation.

Bilateral act

A legal act requiring two concordant wills. A contract.

Bill

A proposed statute, before adoption. Not law, and frequently reported as though it were.

BIP

Bitcoin Improvement Proposal. The formal process for proposing, discussing and adopting changes to the protocol, wallet standards or peer-to-peer communication. Proposals are numbered, publicly reviewed and classified as standards track, informational or process.

BIP141

The proposal that activated segregated witness in 2017. It moved signature data outside the base transaction, fixed transaction malleability and introduced the weight model that discounts witness data.

BIP32

The standard defining hierarchical deterministic wallets, in which an entire tree of key pairs is derived from a single master seed. It is the reason one backup can restore every address a wallet has ever used.

BIP340

The proposal defining Schnorr signatures for Bitcoin, activated as part of Taproot. It enables key aggregation, which allows several signatures to be combined into one.

BIP39

The standard defining how wallet entropy is encoded as twelve or twenty-four words drawn from a fixed wordlist. The most portable and widely supported backup format, and the thing people mean by a seed phrase.

BIP44

Extends BIP32 with a five-level derivation path structure, enabling multiple accounts and currencies while remaining interoperable, so that a wallet backed up in one application can be recovered in another.

Bitcoin address

A string derived from a public key or a spending script, used as a destination for payments. Different encoding schemes produce visually distinct formats identifiable by their prefix.

Bitcoin maximalist

A person who holds that Bitcoin is the only credible decentralised monetary network and that other cryptocurrencies are redundant or harmful. Often shortened to maxi.

Block

A set of validated transactions grouped together and added to the chain. Each block references the one before it, which is what makes the sequence tamper-evident.

Block reward

The incentive paid to the miner of a block, consisting of newly issued bitcoin plus the fees of the transactions included. The newly issued portion is called the subsidy and falls by half at each halving.

Blockchain analytics

The practice of analysing the public transaction graph to trace flows of funds, group addresses believed to belong to one entity, and attribute activity to real-world identities. Sold as a service to exchanges and to law enforcement. Also called chain analysis.

BOLT11 invoice

The standard format for a Lightning payment request. It encodes the recipient node, the amount, a payment hash and an expiry, and is usually presented as a string beginning with a recognisable prefix or as a QR code.

Burden of proof

The obligation to establish a fact. If it is not discharged, the party bearing it loses on that point. Distinguish the legal burden, which does not shift, from the evidential burden, which does.

Bylaw

A rule made by a local authority or by a private body such as a company or association, under a power granted to it.

C

Cantillon effect

The observation, attributed to Richard Cantillon, that newly created money benefits whoever receives it first, before the resulting price rises reduce the purchasing power of everyone else.

Capacity to exercise rights

The ability to act validly on one's own behalf: to contract, to sell, to litigate. Restricted for minors and protected adults, who act through a representative.

Capacity to hold rights

The ability to be a subject of legal relations at all. Every person has it. A newborn can own property while being unable to sell it.

Case law

The body of judicial decisions. A formal source of law in common law systems; formally not one in civil law systems, though highly authoritative in practice.

Cassation

Review by a supreme court limited to questions of law, typically quashing a judgment and returning the case for rehearing rather than substituting its own decision.

Causation

The link between a wrongful act and the harm claimed. One of the three elements of extra-contractual liability, and frequently the real battleground in a case that appears to be about fault.

Cause

In civil law contract, the lawful reason for an obligation. Addressing a broadly comparable question to consideration, namely which promises the law will enforce, though the two doctrines are not equivalents and do not map onto each other cleanly in common law, though the tests differ.

Caveat emptor

Let the buyer beware. The historic default that a buyer bears the risk of defects, now heavily displaced by consumer protection and implied warranties.

Certiorari

A term covering two distinct things that should not be confused. Historically, a supervisory writ by which a superior court calls up a decision of a lower court or public body for review, a function that survives in some common law jurisdictions and has been replaced by a statutory review procedure in others. Separately, in the United States, the discretionary mechanism by which the Supreme Court selects the cases it will hear. The procedures are unrelated in function.

Chain of custody

The documented sequence of who held a piece of evidence and when. Establishing it is often necessary before the evidence can be relied on.

Chain reorganisation

A situation in which a different chain becomes the one with the greatest accumulated proof of work, so that previously confirmed blocks are replaced. Nodes follow the heaviest chain. Commonly shortened to reorg.

Change output

When a transaction spends an output, any value not sent to the recipient returns to the sender as a change output, normally to a fresh address in the sender's own wallet. Handling change carelessly is one of the commonest privacy failures.

Charge

Two meanings. A formal accusation in criminal proceedings. Or a security interest over an asset.

Checks and balances

Arrangements giving each branch of government means of restraining the others. Deliberately overlaps with separation of powers rather than complementing it neatly.

Child pays for parent

A fee-bumping technique in which a new transaction spending an unconfirmed output pays a high enough fee to make it worth a miner's while to confirm both it and its low-fee parent together.

Circular

An internal instruction from an authority to its own officials, explaining how it intends to apply a rule. Soft law: it binds nobody outside the administration, though it tells you a great deal about what will happen in practice.

Civil law

Two unrelated meanings. First, the legal tradition descended from Roman law and expressed in codes. Second, the branch of private law covering persons, property, family and obligations. A common law country has civil law in the second sense.

Class action

A procedure allowing one claimant to sue on behalf of a defined group. Availability varies enormously; many systems permit only narrower collective mechanisms.

Clipboard hijacking

Malware that monitors the clipboard and silently replaces a copied Bitcoin address with the attacker's. Because few people verify addresses character by character, it is an effective and common theft method.

Code

A systematic statement of a whole field of law in a single coherent text, aspiring to completeness and internal logical order. More than a compilation of existing rules.

Codification

The process of producing a code. The characteristic move of the civil law tradition.

Coinbase transaction

The first transaction in a block, which creates the new coins paid to the miner. Unrelated to any company of a similar name.

CoinJoin

A technique in which several independent users combine their inputs and outputs into a single transaction, making it harder for an analyst to determine which input corresponds to which output.

Cold storage

Holding keys on a device that has never been connected to the internet, or is kept permanently offline. The usual arrangement for long-term savings.

Common input ownership heuristic

The assumption, foundational to most blockchain analysis, that all inputs in a single transaction belong to the same owner. CoinJoin and PayJoin are designed specifically to make it unreliable.

Common law

Three meanings. The legal tradition descended from the English royal courts. Judge-made law as opposed to statute. Or, historically, the law of the ordinary courts as opposed to equity.

Compact block relay

A bandwidth optimisation in which a newly mined block is relayed as a header plus short transaction identifiers, allowing peers to reconstruct the block from transactions they already hold.

Competence

The legal power of a body to act on a matter. In federal and supranational systems, disputes about competence frequently decide cases that appear to be about policy.

Concentrated review

Constitutional review monopolised by a single specialised court. The Kelsenian model, common in continental Europe. Contrast diffuse review.

Conciliation

Dispute resolution in which a neutral proposes terms of settlement, going further than a mediator, who only facilitates.

Concurrent powers

Competences both levels of government may exercise in a federal system, with a supremacy rule resolving conflicts.

Condition

A future uncertain event on which the existence or extinction of an obligation depends. Suspensive conditions delay an obligation until the event; resolutory conditions end it if the event occurs.

Confederation

An association of states remaining sovereign, with a joint body exercising only conferred powers which members may reclaim. Historically unstable. A state's name is not evidence of its structure.

Conferral

The principle that a higher level of government holds only the competences expressly conferred on it, with the remainder staying with the members.

Conflict of laws

See private international law.

Conforming interpretation

Preferring, among possible readings, the one consistent with a higher norm, so as to save a provision rather than strike it down. Runs out where the text is unambiguous.

Congruence

The rule-of-law requirement that officials actually apply the rules as announced. The requirement most often absent in practice and the hardest to fix.

Consideration

In common law contract, something of value given in exchange for a promise, generally required for the promise to be enforceable. The requirement has significant exceptions and qualifications, including promises made by deed, promissory estoppel, and the treatment of pre-existing duties and contract modifications, and the detail differs between common law jurisdictions.

Consolidated version

The text of an instrument incorporating all amendments to date. Always the version you want. Reading the original of an amended instrument is a common and avoidable error.

Constituent power

The authority to make a constitution. Original constituent power creates a new order from outside any legal framework; derived constituent power amends under the existing procedure.

Constitution

The founding text or set of norms of a legal order: constituting institutions, allocating and limiting power, and usually guaranteeing rights.

Consultation

The stage at which a draft rule is published for comment. Where legally required, skipping it or treating it as a formality can invalidate the eventual rule.

Contra proferentem

Ambiguity in a contract is interpreted against the party who drafted it. Applied mainly to standard-form and consumer contracts.

Contract

An agreement between parties creating enforceable obligations. Classically requires consent, capacity, a determinate lawful object, and a lawful cause or consideration.

Costs

The expenses of litigation. Systems differ on whether the loser pays the winner's costs, which changes the risk of suing dramatically.

Counterclaim

A claim brought by a defendant against the claimant in the same proceedings.

Criminal law

The branch defining punishable conduct and its penalties. Classified as public law because the state prosecutes on behalf of society, which is why a victim generally cannot drop charges.

Custodial wallet

An arrangement in which a third party holds the private keys on the user's behalf. How that is characterised legally varies considerably: depending on the jurisdiction, the terms of service and how the assets are held, a customer may be an unsecured creditor of the firm, a beneficiary under a trust or similar arrangement, or the owner of identifiable assets held on their behalf. The characterisation is what determines the outcome in an insolvency, and it is worth establishing before it matters rather than after.

Custom

A practice treated as binding through long observance. Requires both consistent practice and a conviction that it is obligatory. Marginal domestically, dominant in international law.

Cypherpunk

A movement originating in the late 1980s advocating the use of cryptography and privacy technology to secure individual autonomy against institutional power. Bitcoin emerged directly from its mailing lists.

D

Damages

Money awarded to compensate loss. The classical principle is full reparation: no more and no less than the loss actually suffered.

De facto

In fact, whatever the legal position. A de facto director is someone who acts as one without being formally appointed.

De jure

As a matter of law, whatever the practical reality.

De lege ferenda

Concerning the law as it should be. Contrast de lege lata, the law as it currently stands. Keeping the two apart is the whole of the positivist discipline.

Decentralisation

Transfer of responsibility to locally elected bodies with their own competences and mandate. Distinguish from deconcentration.

Declaration

A remedy consisting of an authoritative statement of the legal position, without any order to do anything. Useful where parties need certainty rather than compulsion.

Deconcentration

Posting central government officials to the regions, where they remain answerable to the capital. Not the same as decentralisation, though the two often coexist.

Decree

A form of delegated legislation made by the executive. Binding like a statute but valid only within its enabling power.

Default rule

A rule applying unless the parties agree otherwise. Most of contract law is default. Contrast mandatory rule.

Defendant

The party against whom a claim is brought. Also called the respondent in some procedures.

Delegated legislation

Rules made by the executive under authority conferred by statute. Decrees, orders, regulations, statutory instruments. In volume it dwarfs primary legislation.

Delict

The civil law term for a civil wrong outside contract. Equivalent in function to tort.

Derivation path

A specification describing how child keys are deterministically derived from a master seed. Two wallets using different paths from the same seed will show different addresses, which is a frequent cause of an apparently empty wallet.

Derogation

A departure from a rule, permitted in defined circumstances. In human rights law, the temporary suspension of certain rights during a genuine emergency.

Devolution

Statutory transfer of substantial legislative power from a unitary state to a region. Genuine power, resting on ordinary law rather than constitutional guarantee. Often asymmetric.

Diamond hands

Informal term for holding through severe price falls without selling.

Difficulty adjustment

The periodic recalibration of mining difficulty, roughly every two weeks, so that blocks continue to be found at approximately ten-minute intervals regardless of how much mining power has joined or left.

Diffuse review

Constitutional review exercisable by any court in a case before it. Contrast concentrated review.

Digital signature

A mathematical proof attached to a transaction demonstrating that the sender controls the corresponding private key, without revealing the key. It is what allows authorisation on a public network without a trusted intermediary.

Directive

In EU law, an instrument obliging member states to achieve a result, requiring national legislation to implement it. Produces different national laws taking effect on different dates. Contrast a regulation, which applies directly.

Disclosure

The pre-trial stage in which parties must produce relevant documents to each other. Long and expensive in adversarial systems, and a major driver of litigation cost.

Discretion

A choice left to an authority by a rule. Never unlimited: it must be exercised for the proper purpose, on relevant considerations, genuinely case by case, and proportionately.

Distinguishing

Holding that an earlier precedent turned on materially different facts and therefore does not apply. Available to any court, including one otherwise bound. How the common law evolves without admitting error.

Doctrine

The writing of legal scholars. Not a formal source of law, but influential, particularly in civil law systems where treatises shape whole fields.

Domicile

The place a person is legally attached to for various purposes. Definitions differ sharply between systems, and it frequently determines which court has jurisdiction.

Double jeopardy

The prohibition on being tried or punished twice for the same facts in proceedings that are criminal in substance. Why the classification of administrative sanctions as punitive matters.

Double spending

Spending the same bitcoin more than once. Preventing it without a central ledger keeper is the problem Bitcoin was designed to solve.

Dualism

The doctrine that international and domestic law are separate orders, so a treaty has no domestic effect until transposed by statute. Contrast monism.

Due process

The cluster of procedural protections owed before an adverse decision: notice, a hearing, an impartial decision-maker, reasons, and a route of challenge.

Duress

Illegitimate pressure vitiating consent and rendering an agreement voidable.

Dusting attack

Sending tiny amounts to many addresses so that, when the recipients spend them, analysts can link those addresses together and potentially identify their owner.

E

ECDSA

Elliptic Curve Digital Signature Algorithm. The signature scheme used in Bitcoin from the outset and still in use for the older output types. Taproot outputs use Schnorr signatures instead, so both schemes are in active use rather than one having replaced the other. A transaction is signed with a private key and verified by anyone holding the corresponding public key.

Eclipse attack

An attack that isolates a node from honest peers, so that the attacker controls the entire view of the network that the node receives.

Effects doctrine

The basis for regulating conduct occurring abroad that produces consequences within the territory. The foundation of most extraterritorial regulation, and contested because it has no natural limit.

Ejusdem generis

Of the same kind. The rule that general words following a list of specific ones are limited to the same class as those specifics.

Elliptic curve cryptography

Public-key cryptography based on elliptic curves over finite fields. It provides strong security with comparatively small keys, which is why Bitcoin uses it.

Enabling power

The statutory provision authorising the executive to make delegated legislation. Its scope determines the validity of everything made under it, and finding it is the first step in testing any decree.

Enforcement

Converting a judgment into an actual result: seizure of goods, attachment of accounts or earnings, forced sale. A judgment is not money, and this stage frequently fails.

Entry into force

The date from which an instrument actually applies. Frequently later than adoption, sometimes by years. The most commonly omitted fact in reporting on regulation.

Equality of arms

The fair trial requirement that neither party is placed at a substantial disadvantage relative to the other.

Equity

Two meanings. In the English tradition, a body of principles developed in a separate court to soften the rigidity of the common law, and the origin of the trust. Or, generally, fairness as a corrective to strict rules.

Erga omnes

Toward everyone. An obligation or right effective against the world at large rather than against one identified person.

Error

A mistake about an essential quality, vitiating consent and rendering a contract voidable. Not every mistake qualifies; it must bear on something that determined the agreement.

Estoppel

A common law doctrine preventing a person from asserting something contrary to a position they previously took and on which another relied. Functionally close to good faith and legitimate expectations in civil law systems.

Evidence

The material by which facts are established: documents, testimony, expert reports, physical and electronic records, admissions, inspection.

Ex ante

Before the event. Ex ante regulation sets rules in advance; ex post enforcement responds after the fact.

Ex nunc

From now on. An annulment ex nunc operates only for the future, leaving past effects intact. Contrast ex tunc, from the beginning.

Ex officio

By virtue of office, without needing to be asked. A court raising a point ex officio does so on its own motion.

Ex parte

A proceeding heard with only one party present. Exceptional, since it departs from the adversarial principle, and normally used only for urgent measures where notice would defeat the purpose.

Expropriation

Compulsory acquisition of private property by the state for a public purpose, normally requiring due process and compensation.

Extinctive prescription

See limitation.

Extraterritoriality

The application of a state's law to conduct outside its territory.

F

Fault

Conduct falling below the standard of a reasonably prudent person in the circumstances. The basis of most liability, though strict regimes dispense with it.

Federal state

A state with two orders of government, each drawing authority directly from the constitution. The units hold powers the centre cannot remove without constitutional amendment.

Fee market

The competition among users bidding transaction fees for inclusion in the next block. As the subsidy falls with each halving, fees are expected to become the main source of miner revenue.

Fettering discretion

The error of adopting a rigid policy and applying it mechanically, refusing to consider whether an individual case warrants departure. An authority may have a policy but must be willing to hear an argument for an exception.

FOMO

Fear of missing out. The pressure to buy into a rising market for fear of being left behind.

Force majeure

An unforeseeable and irresistible external event excusing non-performance of an obligation.

Forum

The court hearing a case. Its own law is the lex fori.

Forum shopping

Choosing among several available courts the one whose law or procedure is most favourable.

Fraud

Deception inducing agreement, vitiating consent and rendering a contract voidable. Also a criminal offence in its own right.

Fruits

The produce or income of a thing. Natural fruits are crops and offspring; civil fruits are rent and interest. One of the three components of ownership.

FUD

Fear, uncertainty and doubt. Negative or misleading material circulated to provoke selling.

Full node

A computer that stores the chain and independently validates every transaction and block against the rules, requiring no trust in any third party. Running one is the difference between verifying and being told.

Full reparation

The principle that damages restore the victim to the position they would have occupied: no more and no less. The reason punitive damages are controversial in many systems.

G

General principles of law

Principles a legal order treats as inherent without enactment: good faith, the right to be heard, proportionality, legal certainty, nobody may be judge in their own cause.

Genesis block

The first block of the chain, created in 2009.

Good faith

The requirement of honest and loyal conduct in the formation and performance of obligations. A general principle in civil law systems and increasingly recognised elsewhere.

Grandfathering

A transitional provision exempting existing situations from a new rule. Frequently the provision that determines the real impact, and rarely reported.

Guidance

A published statement of how an authority interprets or intends to apply a rule. Soft law: it binds nobody, though it may bind the authority itself through equal treatment or legitimate expectations.

H

Habitual residence

The place where a person has established the centre of their interests. Increasingly preferred over domicile or nationality as a connecting factor, particularly in family and succession matters.

Halving

The event, occurring every 210,000 blocks or roughly every four years, at which the block subsidy is cut in half. It enforces the issuance schedule and continues until the supply cap is reached.

Hard fork

A protocol change that is not backward compatible, so that nodes running the older software reject blocks produced under the new rules. If both chains retain support, two chains with a shared history result.

Hardware wallet

A purpose-built device that stores private keys in isolation and signs transactions internally, so the key never touches an internet-connected machine.

Hash function

A function mapping an input of any size to a fixed-size output, designed to be infeasible to reverse and to make collisions impractical to find.

Hashrate

The total computational power devoted to mining, measured in hashes per second.

Hearsay

Evidence of a statement made outside the proceedings, offered to prove what it asserts. Restricted in some common law systems, generally admitted and simply weighed in civil law systems.

Hierarchy of norms

The ranking of sources of law, in which each draws validity from the one above and cannot lawfully contradict it.

HODL

Holding for the long term regardless of price movement. Originally a misspelling of hold in a forum post.

Horizontal effect

The application of constitutional rights between private parties rather than only against the state. May be direct, where rights bind private parties, or indirect, where courts interpret private law consistently with constitutional values.

HTLC

Hash time-locked contract. The building block of Lightning routing: funds are released only if a secret is revealed within a time limit, and otherwise return to the sender.

Hyperbitcoinisation

A hypothesised scenario in which Bitcoin displaces national currencies and becomes the dominant monetary standard through self-reinforcing adoption. A thesis, not a prediction.

I

Immunity

Exemption from legal process. Judicial immunity protects judges for their decisions; state immunity limits suing foreign states; parliamentary immunity protects legislators for what they say in the chamber.

Impartiality

The requirement that an individual decision-maker has no interest or bias in the particular case, including in appearance. Distinguish from independence, which is structural.

Implied repeal

The abolition of an earlier rule by a later incompatible one, without express words. Courts are reluctant to find it where the texts can be reconciled.

In dubio pro reo

Where doubt remains, decide for the accused. The operational expression of the presumption of innocence.

Independence

The structural freedom of the judiciary from external control, secured by tenure, financial security, independent appointment and discipline, immunity for judicial acts, and rule-based case allocation.

Individual decision

An administrative act applying a rule to a named person. Binding on that person only, and normally challengeable within a short and strictly enforced deadline.

Initial block download

The process by which a new node downloads and independently validates every block from the beginning of the chain to the present, so that it reaches a fully verified state without trusting any peer.

Injunction

A court order to do or refrain from doing something. Often the only useful remedy where harm is ongoing, and available on an interim basis before trial.

Inquisitorial system

A procedural model in which the court directs the proceedings and the search for evidence. Associated with civil law systems. Contrast adversarial.

Instrument

Any formal legal document: a statute, a decree, a treaty, a contract, a deed.

Inter partes

Between the parties. A judgment binds inter partes and, absent precedent, nobody else.

Interim measures

Urgent relief granted before final judgment: freezing assets, suspending a decision, preserving evidence. Decided on a lower standard than full proof, and often where the practical outcome is really determined.

Interpretation

Determining what a legal text means. Classical methods are literal, systematic, historical, teleological and conforming.

Interruption

An event resetting a limitation period to zero, such as commencing proceedings or the debtor acknowledging the debt. Contrast suspension, which merely pauses it.

Irrebuttable presumption

A presumption admitting no contrary proof. Rare, and effectively a substantive rule disguised as an evidential one.

J

Judgment

A court's decision, normally with reasons. Reasoning is generally required because it permits meaningful appeal and disciplines the judge.

Judicial review

Court examination of the lawfulness of legislation or of administrative action. Asks whether a decision was lawful, not whether it was wise.

Jurisdiction

Two meanings. The authority of a court to hear a case, determined by subject matter, territory and level. Or the reach of a state's law generally.

Jurisprudence

Two meanings. In common law usage, legal philosophy. In civil law usage, the body of decided cases. A frequent source of cross-border confusion.

Jurisprudence constante

The civil law doctrine that a consistent line of decisions acquires authority such that departure requires serious justification, without any single decision binding.

Jus cogens

A peremptory norm of international law from which no derogation is permitted, such as the prohibition of genocide or slavery.

L

Legal act

Civil law category for a manifestation of will intended to produce legal effects: a contract, a will, a resignation, an administrative decision. The effects follow because someone wanted them. Contrast legal fact. Common law has no single equivalent term.

Legal aid

Public funding of legal representation for those who cannot afford it. Treated as part of the right of access to a court rather than as charity, because a right that cannot be afforded is theoretical.

Legal certainty

The principle that law should be clear, stable, published and predictable enough for people to plan around it.

Legal fact

Civil law category for an event to which the law attaches consequences regardless of anyone's intention: birth, death, an accident, the passage of time.

Legal person

An entity the law treats as a person: a company, association, foundation, public body, or the state. Owns, contracts, sues and is sued distinctly from those behind it. The foundation of limited liability.

Legal positivism

The view that law is a social fact, valid because produced according to the system's own criteria rather than because it is just. Separates describing the law from evaluating it.

Legal realism

The view that what decides cases is the behaviour of officials rather than the content of rules, so law is best studied through decisions.

Legality, principle of

Two applications. In criminal law, no offence and no penalty without a prior defining law. In administrative law, every exercise of public power requires a legal basis.

Legitimate expectations

The principle that where an authority has induced reliance on a position, abrupt reversal may be unlawful, or may require a transition period or compensation.

Lex fori

The law of the court hearing the case.

Lex loci delicti

The law of the place where the wrong occurred. A common connecting factor for non-contractual liability.

Lex posterior derogat legi priori

The later rule prevails over the earlier, between rules of equal rank.

Lex rei sitae

The law of the place where the property is situated. The usual connecting factor for rights over immovable property.

Lex specialis derogat legi generali

The specific rule prevails over the general one within its field, without repealing it elsewhere. Usually beats the later-rule maxim, contrary to most people's instinct.

Lex superior derogat legi inferiori

The higher rule prevails over the lower.

Lightning Network

A payment network built on top of Bitcoin that enables fast, low-fee payments by routing them through channels, with only the opening and closing recorded on the chain.

Limitation

The period after which a claim can no longer be brought. Also called extinctive prescription. Justified by legal certainty and the impossibility of defending stale allegations.

Liquidated damages

A sum fixed in advance by the contract as payable on breach. Enforceable if a genuine estimate of loss; many systems allow a court to reduce it if manifestly excessive.

Locus standi

See standing.

M

Mandate

The authority given to one person to act on another's behalf. The civil law counterpart to agency.

Mandatory rule

A rule applying regardless of what the parties agree. Consumer and employment protections are typically mandatory, and a clause purporting to exclude them is simply void. Contrast default rule.

Mediation

Dispute resolution in which a neutral facilitates agreement without deciding. Confidential, and increasingly a mandatory first step before litigation.

Mempool

A node's pool of valid but unconfirmed transactions awaiting inclusion in a block. Each node maintains its own, so there is no single canonical mempool.

Mens rea

The mental element of an offence: intention, knowledge, recklessness or negligence, depending on the crime. Most serious offences require it, and its absence is a defence.

Merkle root

The single hash at the top of a Merkle tree, committing to every transaction in a block. It is what allows a specific transaction to be proved to be in a block without the whole block.

Merkle tree

A tree in which each leaf is a hash of data and each parent is a hash of its children, allowing efficient proof that a particular item belongs to the set.

Minimum core

The doctrine that whatever the resource constraints, a state may not fall below a basic threshold in delivering social rights.

Mining

The process of assembling transactions into blocks and competing to find a valid proof of work, thereby extending and securing the chain.

Mining pool

An arrangement in which miners combine their computational power and share the rewards in proportion to the work contributed, smoothing what would otherwise be highly irregular income.

Monism

The doctrine that a ratified treaty becomes part of domestic law automatically and can be invoked before national courts. Contrast dualism.

Mortgage

A real right over immovable property securing a debt. Follows the property into the hands of a buyer, which is what makes it worth more than a promise.

Multisignature

A spending condition requiring a specified number of signatures out of a larger set. Frequently shortened to multisig, and widely used for shared control and inheritance arrangements.

Mutatis mutandis

Applying a provision to a different situation with the necessary changes made.

N

Nakamoto consensus

The combination of proof of work with the rule that nodes follow the chain with the greatest accumulated work, producing agreement without any central authority.

Naked assessment

A tax assessment made without any evidentiary foundation. Where an assessment is arbitrary in this sense, it does not attract the presumption of correctness, and the authority must show a minimal evidentiary link before the burden falls on the taxpayer.

Natural law

The view that principles of justice exist independently of human enactment, and that human law derives its authority from conformity to them.

Negligence

Failure to exercise the care a reasonably prudent person would in the circumstances. The commonest basis of civil liability.

Negotiorum gestio

Voluntary management of another's affairs without a mandate, in that person's interest. Recognised in civil law systems, largely absent from the common law.

Nemo judex in causa sua

Nobody may be judge in their own cause. The foundation of impartiality and of conflict-of-interest rules.

Non bis in idem

Not twice for the same thing. See double jeopardy.

Nonce

A value a miner varies while searching for a block hash below the difficulty target.

Non-custodial wallet

An arrangement in which the user holds their own private keys, and therefore both the control and the entire responsibility.

Non-derogable right

A right that cannot be suspended even during a declared emergency, such as the prohibitions of torture and slavery.

Notary

In civil law systems, a public officer who authenticates documents, advises parties impartially, and holds originals. Documents they draw up carry heightened evidential force and are often required for property transfers and wills.

Novation

Replacing an existing obligation with a new one, extinguishing the first. Distinguish from assignment, which transfers the same obligation.

Nullity

Invalidity of a legal act. Absolute nullity protects the public interest and is void from the outset; relative nullity protects a party and is voidable at their request.

Nullum crimen, nulla poena sine lege

No crime and no penalty without a prior law. The foundational principle of criminal law, entailing non-retroactivity, precision, strict construction and the prohibition of analogy.

O

Obiter dictum

An observation in a judgment not essential to the outcome. Persuasive but not binding. Contrast ratio decidendi.

Objective law

Civil law term for the body of legal rules, as distinct from the subjective rights individuals hold under them.

Obligation

A legal bond by which a debtor owes a performance to a creditor. Three elements: two parties and an object.

Obligation of means

An obligation to exercise diligent effort toward an outcome rather than to achieve it. A doctor or a lawyer owes means. Breach requires proving the effort was inadequate.

Obligation of result

An obligation to achieve a specific outcome. Failure is breach without more. A carrier promising delivery owes a result.

Official journal

The state publication in which laws and decrees appear. Publication there is normally a condition of validity, not a formality.

Ombudsman

An independent body investigating complaints against public authorities or, in sector schemes, against firms. Usually free, often binding on the firm but not the complainant.

Onion routing

In Lightning, a mechanism in which payment instructions are layered and encrypted so that each intermediate node learns only the previous and next hop, not the full route or the parties.

Onus

See burden of proof.

Opinio juris

The conviction that a practice is legally obligatory. The psychological element required for a practice to become custom. Without it, a practice is merely a habit.

Overriding mandatory rules

Rules a forum applies regardless of the law otherwise designated by its conflict rules, because it regards them as essential to its own order.

Overruling

A court of sufficient rank declaring an earlier decision wrong, so that it ceases to be law. Contrast distinguishing.

Ownership

The fullest real right over a thing, classically comprising use, enjoyment of fruits and disposal. Nowhere absolute: limited by planning, neighbour law, expropriation and the prohibition of abusive exercise.

P

P2PKH

Pay to public key hash. The original address format, beginning with the digit one. Widely supported, and more expensive to spend than newer formats.

P2SH

Pay to script hash. An address format beginning with the digit three that commits to a spending script as a hash, so that the script is revealed only when the funds are spent.

P2TR

Pay to Taproot. The address format introduced with Taproot in 2021, enabling Schnorr signatures and making simple and complex spending conditions look alike on the chain.

P2WPKH

Pay to witness public key hash. The native segregated witness address format, offering lower fees and better error detection than the legacy formats.

Pacta sunt servanda

Agreements are to be kept. The foundational principle of contract and of treaty law alike.

Paper hands

Informal term for selling quickly during a fall in price.

Parliamentary system

A system in which the government emerges from the legislature and survives only while retaining its confidence.

Party autonomy

The principle that persons may arrange their own affairs by agreement, within limits set by mandatory rules. The defining feature of private law.

Passphrase

An optional extension to a seed phrase: a user-chosen string added before key derivation, which produces an entirely different wallet from the same words. It adds a layer of security and creates a corresponding risk, since it cannot be recovered from the seed alone.

PayJoin

A transaction in which both sender and receiver contribute inputs, breaking the assumption that all inputs belong to one owner and making the payment substantially harder to trace.

Payment channel

A two-party arrangement secured by an on-chain transaction, within which the parties can transact repeatedly off-chain, recording only the opening and the closing on the chain.

Penalty clause

A contractual sum payable on breach. Enforceable where a genuine estimate of loss; many systems permit reduction if manifestly excessive, and some common law systems refuse to enforce true penalties at all.

Peremptory norm

See jus cogens.

Personal representative

In common law systems, the executor or administrator in whom a deceased person's estate vests. Collects the assets, pays the debts, and distributes what remains to the beneficiaries. Liable only to the extent of the assets that passed through their hands, provided the estate was properly administered. There is no equivalent office in the civil law model of universal succession.

Personal right

A right against one identified person, such as a contractual claim. Does not survive transfer of an asset. Contrast real right.

Personality rights

Rights over one's own person: life, bodily integrity, privacy, image, reputation, name. Not transferable.

Phishing

Impersonating a trusted service through a fake site, email or message to induce someone to reveal a seed phrase, key or credentials. The leading cause of losses in self-custody.

Piercing the veil

Disregarding the separate legal personality of a company to reach those behind it. Exceptional, typically requiring fraud or use of the entity as a façade.

Pledge

A real right over movable property securing a debt, classically involving delivery of the thing to the creditor.

Possession

Factual control of a thing with the intention of holding it as one's own. Protected independently of ownership, to prevent disputes resolving by force.

Preamble

The opening statement of an instrument setting out purpose and context. Sometimes non-binding, sometimes given full legal force by courts, and always useful for interpretation.

Precedent

A prior decision that binds or guides later courts. Binding vertically in common law systems, persuasive in civil law ones.

Pre-image resistance

The property of a hash function that makes it computationally infeasible to recover an input from its output.

Prescription

Civil law term covering two mechanisms. Extinctive prescription extinguishes a claim through the passage of time. Acquisitive prescription creates ownership through prolonged possession. Common law systems reach similar results under the separate labels of limitation and adverse possession.

Presidential system

A system in which the executive is separately elected and does not sit in the legislature, and neither can dismiss the other during a term.

Presumption

A rule directing a court to treat a fact as established from another fact. Rebuttable presumptions shift the burden; irrebuttable ones admit no contrary proof.

Presumption of correctness

In United States tax procedure, the rule that an assessment issued by the revenue authority is presumed correct, so that the taxpayer carries the burden of proving it wrong, including on whether the income existed. Displaced where the assessment is arbitrary and without foundation, and shifted by statute where the taxpayer produces credible evidence and has met substantiation and cooperation requirements. Not a universal rule: other systems place the burden on the authority to establish that income exists.

Presumption of innocence

The rule that an accused person need prove nothing and is treated as innocent until guilt is established to the required standard.

Prima facie

On its face. A prima facie case is one that would succeed unless answered, sufficient to shift the evidential burden.

Primary legislation

Rules adopted by the legislature. Statutes, acts. The highest ordinary source below the constitution.

Private international law

The discipline determining, for cross-border private relationships, which court has jurisdiction, which country's law applies, and whether a judgment will be recognised abroad. Also called conflict of laws.

Private key

The secret value used to sign a transaction. For a single-signature output, whoever holds it can spend the funds. For outputs requiring more than one signature, such as multisignature or Taproot script arrangements, one key alone is not sufficient, and control depends on the spending conditions rather than on any single key. In every case, no legitimate party ever needs to see yours.

Private law

Law governing relationships between persons treated as formally equal. Defined by party autonomy.

Privilege

A protection preventing certain communications from being used as evidence. Lawyer-client privilege exists in essentially every system and belongs to the client, not the lawyer.

Procedural law

Law defining how rights are asserted: which court, within what time, in what form, with what evidence. Underestimated: the commonest way to lose a good case is procedural.

Promulgation

The formal act, usually by the head of state, certifying a law and ordering its publication.

Proof of work

A consensus mechanism in which producing a valid block requires demonstrably expensive computation, making it costly to rewrite history.

Proportionality

The test for whether a limitation on a right is permissible: legal basis, legitimate aim, suitability, necessity, and balance. Necessity is where most measures fail, and the step most worth invoking.

Prospective overruling

Announcing a change in the law while applying the old rule to the present case, or setting a future date for the change, to protect reliance.

Public key

The value derived from a private key that can be shared freely and used by anyone to verify a signature made with the corresponding private key.

Public law

Law governing the relationship between the state and everyone else, and the internal organisation of the state. Defined by inequality of the parties.

Public policy

The ground on which a court may refuse to apply foreign law or recognise a foreign judgment incompatible with its own fundamental values.

Q

Qualification

Characterising established facts in legal terms: deciding whether conduct amounts to negligence, whether an arrangement is a lease or a sale, whether a worker is an employee. The hidden heart of legal work, and where most disputes actually lie.

Quantum

The amount of damages, as opposed to whether liability exists at all. Trials are frequently split into liability and quantum stages.

Question of fact

A question about what happened. Determined at first instance and generally not reviewable by a supreme court.

Question of law

A question about what a rule means. Reviewable at every level.

Quorum

The minimum number of members required for a body to act validly. Also, in multisignature arrangements, the number of keys required to authorise.

R

Ratification

Two meanings. The formal act by which a state consents to be bound by a treaty. Or the approval of an unauthorised act by the person on whose behalf it was done, which validates it retroactively.

Ratio decidendi

The reasoning essential to a judgment's outcome. In common law systems, this is what binds later courts. Separating it from obiter is a core professional skill.

Real right

Civil law category for a right good against the world, over a thing: ownership, usufruct, servitude, mortgage, pledge. Survives transfer of the asset. Contrast personal right. Common law does not use the term but draws a comparable line between proprietary and personal interests.

Reasons, duty to give

The requirement that a decision state why, specifically enough to allow it to be challenged. An unreasoned decision is frequently annullable on that ground alone.

Rebuttable presumption

A presumption the other party may disprove. Shifts the burden without deciding the point.

Recital

An introductory paragraph of an instrument explaining purpose and context. Not usually binding, but used to interpret the operative provisions.

Recognition

Two meanings. Acceptance by one state that an entity is a state. Or acceptance by one country's courts that a foreign judgment has effect there.

Regulation

Two opposite meanings. In the United States and many systems, delegated legislation made by an agency, ranking below a statute. In EU law, a directly applicable act of the Union legislature, functioning as primary legislation. A frequent source of cross-border confusion.

Regulator

A body that supervises a sector and enforces the rules applying to it. Not necessarily a government department: depending on the sector and country a regulator may be a ministry, an independent statutory authority, a central bank, or a self-regulatory organisation recognised by statute. Which body supervises a given firm depends on its licence and its jurisdiction, and is worth establishing rather than assuming.

Relative nullity

Civil law category of invalidity protecting a particular party. The act is valid until annulled, only the protected party may seek annulment, and they may instead confirm it. Roughly comparable to a voidable contract at common law.

Remedy

What a court can order once a breach is established: damages, specific performance, injunction, termination, restitution, annulment, or a declaration.

Repeal

The abolition of a rule. Express where stated; implied where a later incompatible rule displaces it.

Replace-by-fee

A mechanism allowing a sender to broadcast a replacement for an unconfirmed transaction paying a higher fee. Useful for unsticking a transaction, and a reason for a recipient to wait for confirmation.

Replay attack

Reusing a valid transaction in a different context, a risk that arises particularly after a chain split.

Res judicata

The principle that a final judgment cannot be relitigated between the same parties on the same subject. What allows disputes to end.

Rescission

Undoing a contract and returning what was exchanged.

Reserved domain

Subjects a constitution requires to be regulated by statute rather than by the executive: typically crimes and penalties, taxation, fundamental rights, nationality and property. A decree intruding into it is unlawful whatever its content.

Residual powers

Competences not enumerated in a federal constitution, assigned by default to a specified level, usually the units. Whoever holds the residue gains structurally over time.

Restitution

Returning a benefit received without legal cause.

Retroactivity

Application of a rule to conduct predating it. Generally prohibited, most strictly in criminal law, with the exception that a more favourable criminal law applies retroactively.

RIPEMD-160

A hash function applied after SHA-256 to produce compact 160-bit addresses. The combined operation is known as Hash160 and underlies the legacy address formats.

Rule of law

The principle that power is exercised through law rather than will. A cluster of requirements: generality, publicity, non-retroactivity, clarity, consistency, possibility of compliance, stability, and congruence between announced rules and official action.

Rule of recognition

Hart's answer to the foundation of legal validity: a social practice by which officials accept certain criteria for identifying valid law.

S

Sanction

A penalty for breach. May be criminal, administrative or civil, each with different procedures, standards of proof and protections.

Satoshi

The smallest unit of Bitcoin: one hundred millionth of one bitcoin. Often shortened to sat.

Schnorr signature

A signature scheme introduced with Taproot, offering better efficiency and privacy and allowing several signatures to be aggregated into one.

Script

Bitcoin's scripting language. The locking script sets the conditions for spending an output and the unlocking script satisfies them, which is what makes conditional spending possible.

Security interest

A real right over an asset securing an obligation: mortgage, pledge, charge, lien. Gives priority over unsecured creditors on insolvency.

Seed phrase

The ordered list of words from which every key in a wallet is derived. It is the wallet. Anyone who reads it can spend the funds, and no legitimate party ever needs it.

SegWit

Segregated witness. The 2017 upgrade that moved signature data outside the base transaction, fixing transaction malleability and providing the foundation for the Lightning Network.

Selfish mining

A strategy in which a miner withholds a block it has found and continues mining privately, aiming to make honest miners waste work and so gain a disproportionate share of rewards.

Separation of powers

The division of state power among legislative, executive and judicial functions exercised by distinct institutions. A standard for assessing arrangements rather than a description of any actual state.

Service

Formal delivery of proceedings to a defendant. A defendant never properly served can usually have the resulting judgment set aside, sometimes years later.

Servitude

Civil law real right burdening one property for the benefit of another, such as a right of way. Binds successive owners. The common law equivalent is an easement.

Set-off

Extinguishing mutual debts against each other so that only the balance is owed.

Severability

The principle that an invalid clause or provision may be struck out while the rest survives, provided the remainder still makes sense.

SHA-256

The hash function used in Bitcoin's proof of work, producing a 256-bit output.

Simplified payment verification

A method allowing a lightweight client to check that a transaction is in a block using only block headers, rather than the full chain. Convenient, and weaker than validating for yourself.

Soft fork

A backward-compatible upgrade in which updated nodes enforce stricter rules while nodes that have not upgraded still accept the resulting blocks.

Soft law

Guidance, circulars, recommendations, opinions, supervisory expectations and codes. Binds nobody, yet frequently determines behaviour. May bind the issuing authority through equal treatment or legitimate expectations.

Sound money

Money whose supply is difficult to manipulate and which therefore holds its purchasing power. The property Bitcoin is designed to provide by protocol rather than by discretion.

Sources of law

The recognised origins of legal rules: constitution, legislation, delegated legislation, case law, international law, custom, general principles.

Sovereignty

Supreme authority within a territory and independence from other states. In practice a bundle of powers that can be pooled, delegated and reclaimed.

Specific performance

An order to perform an obligation as promised. The primary remedy in civil law systems, exceptional in common law ones where damages come first.

Stale block

A valid block found at the same height as another that the network accepted first. It is discarded and earns its miner nothing. Sometimes called an orphan.

Standard of proof

The degree of certainty required to establish a fact. Very high in criminal matters, lower in civil ones.

Standing

The right to bring a claim, generally requiring a personal, direct and current interest. Many claims fail here without the merits being examined.

Stare decisis

The common law doctrine of standing by decided matters. Binds vertically, and to varying degrees horizontally.

Statute of limitations

See limitation.

Statutory instrument

A form of delegated legislation, particularly in the United Kingdom.

Stratum protocol

The protocol by which mining pools distribute work to miners and collect the results. Its second version allows miners to choose their own transaction sets, which distributes a decision previously made by the pool.

Strict liability

Liability attaching without proof of fault, based on a risk created: defective products, dangerous activities, things in one's custody, employees' acts.

Subjective right

Civil law term for an entitlement an individual holds under the objective law, classified as real, personal, intellectual or personality rights. English has no clean equivalent pairing, which is a recurring source of translation difficulty.

Subsidiarity

The principle that decisions should be taken at the lowest level capable of achieving the objective adequately.

Substantive law

Law defining rights and obligations. Contrast procedural law, which defines how they are asserted.

Supranational organisation

An organisation to which states have transferred competences, whose acts can bind directly and take precedence over conflicting national law within those competences.

Suspension

Two meanings. Pausing a limitation period, which then resumes where it stopped. Or halting the effect of a decision pending challenge.

Sybil attack

An attack in which one party creates many apparent identities in order to exert disproportionate influence on a network.

Systematic interpretation

Reading a provision in the context of the instrument as a whole and of the wider legal order.

T

Teleological interpretation

Interpreting a rule so as to achieve its purpose. Dominant in modern practice, and the method best suited to circumstances the drafters never imagined.

Territoriality

The default basis of jurisdiction: a state's law applies within its territory.

Testator

A person who makes a will.

Third party

Someone who is not a party to a contract or proceeding. Contracts bind the parties; making them effective against third parties usually requires publicity such as registration.

Timelock

A condition preventing an output from being spent until a specified time or block height. Widely used in inheritance and escrow arrangements.

Tor

An anonymity network that Bitcoin software supports natively, allowing a node to communicate without revealing its network address.

Tort

Extra-contractual civil wrong giving rise to a duty to repair harm. Called delict in civil law systems.

Transaction

A signed instruction transferring bitcoin. It consumes previous unspent outputs as inputs and creates new outputs.

Transitional provisions

Provisions governing how a new rule treats situations already under way. Frequently the provisions that determine the real impact, and rarely reported.

Transposition

Converting a supranational instrument into national law by enacting domestic measures that give it effect. The term belongs to systems that participate in such an order, principally European Union member states transposing a directive, and has no counterpart in a jurisdiction that is not party to one.

Treaty

A binding agreement between states. Its domestic effect depends on whether the system is monist or dualist.

Trust

An arrangement, originating in equity, by which one person holds property for the benefit of another. Central to common law asset planning, with no exact civil law equivalent.

U

Ultra vires

Acting beyond one's powers. The most frequently successful ground of challenge in administrative law.

Unicameral

A legislature with a single chamber.

Unified credit

An arrangement in which gift tax and estate tax share a single cumulative exemption, so that every taxable lifetime gift permanently reduces the amount available at death, with no lookback period. Used in the United States. Contrast systems that instead pull back only gifts made within a defined window before death.

Unilateral act

A legal act requiring only one will: a will, a resignation, an administrative decision.

Unitary state

A state with one source of sovereign authority, in which sub-national powers are granted and revocable by ordinary law. Not the same as centralised.

Universal succession

The civil law rule that heirs succeed to the whole legal position of the deceased, assets and debts together, vesting directly at death. Because an heir can be personally liable for debts exceeding the assets, these systems provide for acceptance limited to net assets, or renunciation. Common law does not work this way: the estate is administered by a personal representative and beneficiaries are not personally liable for the deceased's debts.

Universality of the estate

See universal succession.

Unjust enrichment

The duty to restore a benefit received without legal cause at another's expense. The residual remedy when nothing else fits.

Usufruct

A real right to use a thing and take its fruits while another holds the bare ownership. Widely used in estate planning in civil law countries.

UTXO

Unspent transaction output. The basic unit of account in Bitcoin. A balance is not a number stored anywhere; it is the sum of the unspent outputs a wallet can spend.

UTXO consolidation

Combining several small unspent outputs into fewer larger ones, reducing future fees but publicly linking the addresses involved. A real trade-off between cost and privacy.

V

Validity

Whether a legal act or instrument satisfies the requirements for legal effect. Distinct from existence, and from enforceability against third parties.

VASP

Virtual asset service provider. A category defined by the Financial Action Task Force covering businesses that exchange, transfer or hold virtual assets for others. VASPs are the entities on which anti-money laundering and travel rule obligations are usually imposed.

vByte

Virtual byte. The unit of transaction size introduced with segregated witness, under which witness data counts for less than other data. Fees are quoted in satoshis per virtual byte.

Veto

An executive power to block or delay legislation adopted by the legislature.

Vicarious liability

Liability of one person for the acts of another, most commonly an employer for an employee acting within their functions.

Vitiated consent

Consent affected by error, fraud or duress, rendering an agreement voidable at the request of the affected party.

Void

Without legal effect from the outset.

Voidable

Valid until annulled at the request of a protected party, who may instead confirm the act.

W

Waiver

Voluntarily giving up a right. Cannot extend to rights protected by mandatory rules, which is why many waiver clauses are unenforceable.

Warranty

A contractual assurance about a quality or state of affairs, breach of which gives a remedy without needing to prove fault.

Watch-only wallet

A wallet holding only an extended public key, able to display balances and generate addresses but unable to spend. Useful for monitoring cold storage from an ordinary computer.

Watchtower

A service that monitors the chain for a Lightning participant who is offline and, if a counterparty publishes an outdated channel state, publishes the penalty transaction on their behalf.

Whale

A holder large enough that their trading can move the market.

Will

A unilateral legal act disposing of a person's estate on death. Subject to strict formal requirements in most systems, and generally revocable until death.

Without prejudice

Two meanings. In a legal text, that a provision does not displace another rule. In correspondence, that the communication is part of settlement attempts and cannot be used in evidence.

Writ

A formal written command from a court. Historically, the document initiating proceedings in common law systems.

Z

Zero-knowledge proof

A method by which one party can prove they know something without revealing what it is. Relevant to privacy research and to second-layer protocols.