What is "ne bis in idem"

phr. (context legal English) The concept that no legal action can be instituted twice for the same cause.

Non bis in idem, which translates literally from Latin as "not twice in the same [thing]", is a legal doctrine to the effect that no legal action can be instituted twice for the same cause of action. It is a legal concept originating in Roman Civil Law, but it is essentially the equivalent of the double jeopardy (autrefois acquité) doctrine found in common law jurisdictions.

The International Covenant on Civil and Political Rights guarantees the right to be free from double jeopardy; however, it does not apply to prosecutions by two different sovereigns (unless the relevant extradition treaty expresses a prohibition). The Rome Statute of the International Criminal Court creates a different form of ne bis in idem.