Definitions are from Black's Law Dictionary, 10th ed., edited by Bryan A. Garner (Thomson Reuters, 2014).
actus reus [Law Latin "guilty act"] The wrongful deed that comprises the physical components of a crime and that generally must be coupled with mens rea to establish criminal liability; a forbidden act <the actus reus for theft is the taking of or unlawful control over property without the owner's consent>.
ad litem [Latin "for the suit"] For the purposes of the suit; pending the suit.
affirmative defense A defendant's assertion of facts and arguments that, if true, will defeat the plaintiff's or prosecution's claim even if all the allegations in the complaint are true. • The defendant bears the burden of proving an affirmative defense. Examples of affirmative defenses are duress (in a civil case) and insanity and self-defense (in a criminal case).
a fortiori [Latin] By even greater force of logic; even more so it follows <if a 14-year-old child cannot sign a binding contract, then, a fortiori a 13-year-old cannot>.
Alien Tort Claims Act A section in the Judiciary Act of 1789 giving federal courts jurisdiction to hear tort claims brought by foreigners who allege a violation of international law or a treaty to which the United States is a party. 28 USCA § 1350. • The statute was largely dormant until the 1980s, when it was invoked in several cases involving torture, disappearances, or killings committed by non-Americans in foreign countries. Later, alien plaintiffs began using the law to sue large corporations and the United States government or those acting at the government's direction. — Abbr. ATCA. — Also termed Alien Tort Statute.
amicus curiae [Latin "friend of the court"] Someone who is not a party to a lawsuit but who petitions the court or is requested by the court to file a brief in the action because that person has a strong interest in the subject matter. — Often shortened to amicus. — Also termed friend of the court. Pl. amici curiae.
archipelago 1.Collectively, related islands that together stud a particular area within a large body of water, the islands forming (or historically having formed) a distinctive geographic, economic, and political entity. 2. The waters in which those islands are located.
aut dedere aut peonam persequi [Latin "extradite or enforce the sanction"] The rule that a sentence handed down by a court against a person who flees or has fled to another country should be enforced by that country if it chooses not to extradite the person.
bay An inlet of the sea, over which the coastal country exercises jurisdiction to enforce its environmental, immigration, and customs laws.
certiorari [Law Latin "to be more fully informed"] An extraordinary writ issued by an appellate court, at its discretion, directing a lower court to deliver the record in the case for review. • The writ evolved from one of the prerogative writs of the English Court of King's Bench, and in the United States it became a general appellate remedy. The U.S. Supreme Court uses certiorari to review most of the cases that it decides to hear. — Abbr. cert. — Also termed writ of certiorari.
civil law (usu. cap.) One of the two prominent legal systems in the Western world, originally administered in the Roman Empire and still influential in continental Europe, Latin America, Scotland, and Louisiana, among other parts of the world; roman law. Cf. common law.
comity A principle or practice among political entities (as countries, states, or courts of different jurisdictions) whereby legislative, executive, and judicial acts are mutually recognized.
common law The body of law based on the English legal system, as distinct from a civil-law system; the general Anglo-American system of legal concepts, together with the techniques of applying them, that form the basis of the law in jurisdictions where the system applies <all states except Louisiana have the common law as their legal system>. Cf. civil law.
consanguinity The relationship of persons of the same blood or origin.
continental shelf The submerged border of a continent where the seabed constitutes a relatively shallow landmass, usu. sloping gradually to a point of steeper descent, extending beyond a state's territorial sea through the natural prolongation of its land territory to the outer edge of the submerged continental margin, or 200 nautical miles from the baselines from which the breadth of the territorial sea is measured, whichever distance is greater.
contra legem [Latin] Contrary to law; against the law.
contiguous zone An area abutting and extending beyond the territorial sea, in which countries have limited powers to enforce customs as well as fiscal, sanitary, and immigration laws.
custom A practice that by its common adoption and long, unvarying habit has come to have the force of law.
de facto Actual: existing in fact; having effect even though not formally or legally recognized <a de facto contract>. Cf. de jure.
de jure Existing by right or according to law <dejure segregation during the pre-Brown era>. Cf. de facto.
de minimis non curat lex The law does not notice or concern itself with trifling matters.
de novo Anew.
dispositive Being a deciding factor; (of a fact or factor) bringing about a final determination.
dolus [Latin "device; artifice"] 1. Conduct intended to deceive someone; bad faith. • Although there may be dolus without fraud, fraud always includes dolus. 2. Intentional aggression; willful injury, esp. to another's property.
dolus directus [Latin] Foresight of and direct desire to produce the primary or direct consequences of an action.
dolus eventualis [Latin] Awareness of the probable outcome of an action.
dolus specialis [Latin] Special deceit.
double criminality The punishability of a crime in both the country where the suspect is being held and the country asking for the suspect to be handed over to stand trial. • Double criminality is a requirement for extradition. — Also termed dual criminality.
erga omnes [Latin] Toward all. See obligations erga omnes.
estoppel 1. A bar that prevents one from asserting a claim or right that contradicts what one has said or done before or what has been legally established as true. 2. A bar that prevents the relitigation of issues.
exclusive economic zone An area just beyond the territorial sea, extending up to 200 nautical miles from the baseline of the territorial sea, in which the coastal country enjoys special authority for economic purposes. — Abbr. EEZ.
exculpate To free from blame or accusation; esp., to prove not guilty. — exculpation, n. — exculpatory, adj.
ex hypothesi [Latin] Hypothetically; by hypothesis; on the assumption <conviction for a felony is ex hypothesi impossible in the case of suicide>.
ex injuria jus non oritur A right does not arise from wrongdoing. [Listed in Black's as ex iniuria ius non oritur.]
ex post facto [Latin "from a thing done afterward"] Done or made after the fact; having retroactive force or effect.
force majeure An event or effect that can be neither anticipated nor controlled; esp., an unexpected event that prevents someone from doing or completing something that he or she had agreed or officially planned to do. • The term includes both acts of nature (e.g., floods and hurricanes) and acts of people (e.g., riots, strikes, and wars).
Foreign Sovereign Immunities Act A federal statute providing individuals with a right of action against foreign governments, under certain circumstances, to the extent the claim arises from the private, as opposed to the public, acts of the foreign state.
forum prorogatum [Latin] Hist. The deferred forum.
freedom of the seas The principle that the seas beyond territorial waters are not subject to any country's control. • Ships on the high seas are subject only to the jurisdiction of the country whose flag they fly, except in cases of piracy, hijacking, hot pursuit from territorial waters, slave trading, and certain rights of approach by warships. — Also termed mare liberum
high seas The ocean waters beyond the jurisdiction of any country. • Under traditional international law, the high seas began 3 miles from the coastline. Under the 1982 U.N. Convention on the Law of the Sea, which is generally accepted as international law today, the high seas begin 200 nautical miles form the coastline, outside any country's exclusive economic zone. — Also termed free seas; open seas; main seas.
historic bay A bay that, because of its shape, would not be considered a bay subject to the coastal country's jurisdiction, except for that country's long-standing unilateral claim over it; a bay over which the coastal country has traditionally asserted and maintained dominion.
in absentia [Latin] In the absence of (someone); in (someone's) absence <tried in absentia>.
inculpate 1. To accuse. 2. To implicate (oneself or another) in a crime or wrongdoing. — inculpation, n. — inculpatory, adj.
in limine [Latin "at the outset"] Preliminarily; presented to only the judge, before or during trial <a question to be decided in limine>.
innocent passage The right of a foreign ship to pass through a country's territorial waters; the right of a foreign vessel to travel through a country's maritime belt without paying a toll. • The right of innocent passage is guaranteed in Article 17 of the United Nations Convention on the Law of the Sea. Passage is considered innocent as long as it is not prejudicial to the peace, good order, and security of the coastal country. — Also termed right of innocent passage Cf. transit passage.
instrument of ratification A document formally acknowledging the issuing state's confirmation and acceptance of a treaty, and exchanged by the treaty parties or deposited with a designated state or international organization. See ratification (4).
instrumentum A document, deed, or instrument; esp. a document that is not under seal, such as a court roll.
inter alia [Latin] Among other things.
internal waters Any natural or artificial body or stream of water within the territorial limits of a country, such as a bay, gulf, river mouth, creek, harbor, port, lake, or canal. — Also termed inland waters.
International Law Commission A body created in 1947 by the United Nations for the purpose of encouraging the progressive development and codification of international law. • The Commission is composed of experts in international law. It has drafted many important treaties that have become binding treaty law, including the Vienna Convention on the Law on Treaties. — Abbr. ILC.
ipso jure [Latin "by the law itself"] By the operation of the law itself <despite the parties' actions, the property will revert to the state, ipso jure, on May 1>.
jure gentium By the law of nations.
jure gestionis [Latin "by way of doing business"] A country's acts that are essentially commercial or private, in contrast to its public or governmental acts. • Under the Foreign Sovereign Immunities Act, a foreign country's immunity is limited to claims involving its public acts. The statutory immunity does not extend to claims arising from the private or commercial acts of a foreign state.
jure imperii [Latin "by right of sovereignty"] The public acts that a country undertakes as a sovereign state, for which the sovereign is usu. immune from suit or liability in a foreign country.
jus ad bellum [Latin "right to war"] Criteria to be considered before deciding whether engaging in a war is just.
jus ad rem [Law Latin "right to a thing"] A right in specific property arising from another person's duty and valid only against that person; an inchoate or incomplete right to a thing.
jus in bello [Latin "law in waging war"] The criteria for determining whether the conduct of an ongoing war is just.
jus cogens [Latin "compelling law"] A mandatory or peremptory norm of general international law accepted and recognized by the international community as a norm from which no derogation is permitted.
jus dispositivum [Latin "law subject to the disposition of the parties"] A norm that is created by the consent of participating countries, as by an international agreement, and is binding only on the countries that agree to be bound by it.
legal positivism The theory that legal rules are valid only because they are enacted by an existing political authority or accepted as binding in a given society, not because they are grounded in morality or in natural law.
lex ferenda [Latin] Law proposed for enactment.
lex lata [Latin] The law as it exists; enacted law.
male captus, bene detentus Wrongly captured, well detained.
mens rea [Law Latin "guilty mind"] The state of mind that the prosecution, to secure a conviction, must prove that a defendant had when committing a crime <the mens rea for theft is the intent to deprive the rightful owner of the property>. • Mens rea is the second of two essential elements of every crime at common law, the other being the actus reus [Law Latin "guilty act"].
mutatis mutandis [Latin] All necessary changes having been made; with the necessary changes <what was said regarding the first contract applies mutatis mutandis to all later ones>.
ne bis in idem [Latin] Scots law. Not twice for the same thing. • The phrase usu. referred to the law forbidding more than one trial for the same offense. It essentially refers to the double-jeopardy bar.
non liquet [Latin "it is not clear"] A tribunal's nondecision resulting from the unclarity of the law applicable to the dispute at hand. • In modern usage, the phrase appears almost always in passages stating what a court must not do: tribunals are routinely disallowed from declaring a non liquet.
nonrefoulement A refugee's right not to be expelled from one state to another, esp. to one where his or her life or liberty would be threatened. Cf. refoulement.
note verbal An unsigned diplomatic note, usu. written in the third person, that sometimes accompanies a diplomatic message or note of protest to further explain the country's position or to request certain action. — Also termed note verbale.
nulla peona sine lege [Latin] No punishment without a law authorizing it.
nullum crimen sine lege [Latin] No crime without law.
obiter dictum [Latin "something said in passing"] A judicial comment made while delivering a judicial opinion, but one that is unnecessary to the decision in the case and therefore not precedential (although it may be considered persuasive). — Often shortened to dictum or, less commonly, obiter.
obligations erga omnes [Latin "duties toward all"] A country's duties that concern issues affecting the international community at large, not just the country's neighboring states. — Also termed erga omnes obligations; erga omnes partes obligations.
opinio juris (sive necessitatis) [Latin "opinion that an act is necessary by rule of law"] The principle that for conduct or a practice to become a rule of customary international law, it must be shown that countries believe that international law (rather than moral obligation) mandates the conduct or practice.
pacta sunt servanda [Latin "agreements must be kept"] Treaties (agreements) are to be observed.
pari passu [Latin "by equal step"] Proportionally; at an equal pace; without preference <creditors of a bankrupt estate will receive distributions pari passu>.
political question A question that a court will not consider because it involves the exercise of discretionary power by the executive or legislative branch of government. — Also termed nonjusticiable question.
political-question doctrine The judicial principle that a court should refuse to decide an issue involving the exercise of discretionary power by the executive or legislative branch of government.
Posse Comitatus Act An 1878 federal statute that, with a few exceptions, prohibits the Army or Air Force from directly participating in civilian law-enforcement operations, as by making arrests, conducting searches, or seizing evidence. • The Act does not usu. apply to members of the Navy, the National Guard, or the Coast Guard.
post hoc 1. adv. After this; subsequently. 2. adj. Of, relating to, or involving the fallacy of assuming causality from temporal sequence; confusing sequence with consequence.
precautionary principle The doctrine that when there are threats of serious or irreversible damage to the environment, a lack of full scientific certainty is not a reason for postponing measures to prevent the damage.
prescription 5. The acquisition of title to a thing (esp. an intangible thing such as the use of real property) by open and continuous possession over a statutory period. 6. Int'l law. The acquisition of a territory through a continuous and undisputed exercise of sovereignty over it.
prima facie Sufficient to establish a fact or raise a presumption unless disproved or rebutted; based on what seems to be true on first examination, even though it may later be proved to be untrue <a prima facie showing>.
ratification 4. Int'l law The final establishment of consent by the parties to a treaty to be bound by it, usu. including the exchange or deposit of instruments of ratification <the ratification of the nuclear-weapons treaty>. See instrument of ratification.
ratione materiae By reason of the matter involved.
ratione personae By reason of the person concerned.
rebus sic stantibus [Latin "matters so standing"] The principle that all agreements are concluded with the implied condition that they are binding only as long as there are no major changes in the circumstances.
reductio ad absurdum [Latin "reduction to the absurd"] In logic, disproof of an argument by showing that it leads to a ridiculous conclusion.
refoulement Expulsion or return of a refugee from one state to another. Cf. nonrefoulement.
remand To send (a case or claim) back to the court or tribunal from which it came for some further action <the appellate court reversed the trial court's opinion and remanded the case for new trial>.
reservation 6. The establishment of a limiting condition or qualification; esp., a country's formal declaration, upon signing or ratifying a treaty, that its willingness to become a party to the treaty is conditioned on the modification or amendment of one or more provisions of the treaty as applied in its relations with other parties to the treaty.
res judicata [Latin "a thing adjudicated"] An issue that has been definitively settled by judicial decision.
restrictive principle of sovereign immunity The doctrine by which a foreign country's immunity does not apply to claims arising from the country's private or commercial acts, but protects the country only from claims arising from its public functions.
right of self-determination for peoples The right of the postcolonial populations of the world's countries to be free to decide for themselves how they wish to be governed in a decolonized world. — Often shortened to self-determination.
rule of lenity The judicial doctrine holding that a court, in construing an ambiguous criminal statute that sets out multiple or inconsistent punishments, should resolve the ambiguity in favor of the more lenient punishment. — Also termed lenity rule.
self-determination The right of each culturally homogenous country to constitute an independent state. See right of self-determination for peoples.
self-executing (Of an instrument) effective immediately without the need of any type of implementing action <the wills had self-executing affidavits attached> • Legal instruments may be self-executing according to various standards. For example, treaties are self-executing under the Supremacy Clause of the U.S. Constitution (art VI, § 2) if textually capable of judicial enforcement and intended to be enforced in that manner.
seriatim [Latin] One after another; in a series; successively <the court disposed of the issues seriatim>. — Also termed seriately.
sine qua non [Latin "without which not"] An indispensable condition or thing; something on which something else necessarily depends. — Also termed conditio sine qua non.
stare decisis [Latin "to stand by things decided"] The doctrine of precedent, under which a court must follow earlier judicial decisions when the same points arise again in litigation.
sui generis [Latin "of its own kind"] Of its own kind or class; unique or peculiar.
sustainable development The use of natural resources in a manner that can be maintained and supported over time, taking into account the needs of future generations.
terra nullius [Latin "the land of no one"] A territory not belonging to any particular country.
territorial sea The ocean waters over which a coastal country has sovereignty, extending seaward up to 12 nautical miles from the coastline.
tort A civil wrong, other than breach of contract, for which a remedy may be obtained, usu. in the form of damages; a breach of a duty that the law imposes on persons who stand in a particular relation to one another. • Tortious conduct is typically one of four types: (1) a culpable or intentional act resulting in harm; (2) an act involving culpable and unlawful conduct causing unintentional harm; (3) a culpable act of inadvertence involving an unreasonable risk of harm; and (4) a nonculpable act resulting in accidental harm for which, because of the hazards involved, the law imposes strict or absolute liability despite the absence of fault.
transit passage The right of a vessel or airplane to exercise freedom of navigation and overflight solely for the purpose of continuous and expeditious transit between one part of the high seas or an exclusive economic zone and another part of the high seas or an exclusive economic zone. — Also termed right of transit passage. Cf. innocent passage.
travaux préparatoires [French "preparatory works"] Materials used in preparing the ultimate form of an agreement or statute, and esp. of an international treaty; the draft or legislative history of a treaty.
tribunal A court of justice or other adjudicatory body.
ultra vires [Latin "beyond the powers (of)"] Unauthorized; beyond the scope of power allowed or granted by a corporate charter or by law <the officer was liable for the firm's ultra vires actions>.
uti possidetis The doctrine that the administrative boundaries will become international boundaries when a political subdivision or colony achieves independence.