consuetudinarie

Consuetudinarie is an adjective and noun used to describe rules, practices, or norms that arise from long-standing usage rather than formal enactment. The term derives from consuetudo, Latin for habit or custom, and is often used in phrases such as norme consuetudinarie or diritto consuetudinario to distinguish customary practice from codified law.

In domestic legal systems, customary norms can operate as a source of law or as a guide for interpreting statutes and contracts. Their binding force depends on national tradition and constitutional order; they generally require broad, long-standing practice and a belief that such practice is legally obligatory. Statutes or judicial decisions can modify or override customary rules.

In international law, customary norms—customary international law—emerge from widespread state practice and opinio iuris, the belief that the practice is legally required. These norms fill gaps where no treaty exists and can be jus cogens or non-binding if not universal. On the route to becoming binding, the practice must be general, consistent, and accepted as law by states over time.

They develop gradually as states adopt similar practices; over time, persistent practice accompanied by belief in legal obligation becomes customary law, which can be codified later or remain unwritten.

Examples include long-standing property transfer practices in rural communities, maritime usages of fisheries or navigation, and traditional family or inheritance rules in societies where written law is limited. Consuetudinarie thus describes a form of law or normative force that rests on habitual practice rather than formal legislation.