Customary International Law refers to practices and norms that have developed over time and are accepted as legally binding by states, even if they are not written in formal treaties. These customs arise from consistent state behavior and a belief that such practices are obligatory. Examples include the prohibition of torture and the principle of non-refoulement, which protects refugees. For a custom to be recognized as customary international law, it must meet two criteria: widespread and consistent state practice, and a belief that this practice is legally required, known as opinio juris. This body of law plays a crucial role in international relations and helps maintain order among nations.