Consuetudinary is a term applied to law

Law

Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

 where the rule of law

Rule of law

The rule of law, sometimes called supremacy of law, is a legal maxim that says that governmental decisions should be made by applying known principles or laws with minimal discretion in their application...

 is determined by long-standing custom as opposed to case law

Case law

In law, case law is the set of reported judicial decisions of selected appellate courts and other courts of first instance which make new interpretations of the law and, therefore, can be cited as precedents in a process known as stare decisis...

 or statute

Statute

A statute is a formal written enactment of a legislative authority that governs a state, city, or county. Typically, statutes command or prohibit something, or declare policy. The word is often used to distinguish law made by legislative bodies from case law, decided by courts, and regulations...

.

Most laws of consuetudinary basis deal with standards of community that have been long-established in a given locale. However the term "consuetudinary" can also apply to areas of international law

International law

Public international law concerns the structure and conduct of sovereign states; analogous entities, such as the Holy See; and intergovernmental organizations. To a lesser degree, international law also may affect multinational corporations and individuals, an impact increasingly evolving beyond...

 where certain standards have been nearly universal

Universal jurisdiction

Universal jurisdiction or universality principle is a principle in public international law whereby states claim criminal jurisdiction over persons whose alleged crimes were committed outside the boundaries of the prosecuting state, regardless of nationality, country of residence, or any other...

 in their acceptance as correct bases of action - in example, laws against piracy

Piracy

Piracy is an act of robbery or criminal violence at sea. The term can include acts committed on land, in the air, or in other major bodies of water or on a shore. It does not normally include crimes committed against persons traveling on the same vessel as the perpetrator...

 or slavery

Slavery

Slavery is a system under which people are treated as property to be bought and sold, and are forced to work. Slaves can be held against their will from the time of their capture, purchase or birth, and deprived of the right to leave, to refuse to work, or to demand compensation...

 (see hostis humani generis

Hostis humani generis

Hostis humani generis is a legal term of art that originates from admiralty law. Before the adoption of public international law, maritime pirates and slavers were held to be beyond legal protection, and could be dealt with as seen fit by any nation, even if that nation had not been directly...

). In many, though not all instances, consuetudinary laws will have supportive court rulings and case law that has evolved over time to give additional weight to their rule as law and also to demonstrate the trajectory of evolution (if any) in the interpretation of such law by relevant courts.