Opinio Juris Sive Necessitatis Law and Legal Definition
Opinio juris sive necessitatis means "an opinion of law or necessity.” It is the belief that an action was carried out because it was a legal obligation. This term is frequently used in legal proceedings as a defense in a case.
Opinio juris sive necessitatis is a source of law in domestic and international cases because it deals with beliefs. The action should be consistent and internationally acceptable to qualify as state practice. The principle of International Law is that where states believe and accept that a practice exists and must be followed because of a rule of law requiring it, the practice becomes a part of the body of norms known as International Customary Law.