Consuetudinary

Consuetudinary (Med. Lat. consuetudinarius, from consuetudo: custom), customary, a term applied to law where the rule of law is determined by long-extant customs as opposed to case law or legislative processes leading to novel statutory written law. 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 where certain standards have been nearly universal in their acceptance as correct bases of action—in example, laws against piracy or slavery. 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.

(See also: Oral law, Custom)