Ne bis in idem

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 acquit) 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 non bis in idem.

The Rome Statute establishing the International Criminal Court (ICC) states that the non bis in idem principle has a peculiar meaning, especially if compared to European supranational law. The ICC jurisdiction is complementary to national law, and article 20 of the Rome Statute specifies that, even if the principle shall subsist in general terms, this cannot be taken in consideration in case one of the two conditions (unwillingness and incapability) of existence of the supranational court's jurisdiction occurs. Article 10 of ICTY Statute and article 9 of ICTR Statute state that the non bis in idem principle can be enforced mainly to clarify that the ad hoc tribunal's sentences are "stronger" than the ones in domestic courts. In other words, national courts cannot proceed against the responsible parties of crimes falling in the tribunal's jurisdiction if the international tribunal has already pronounced sentence for the same crimes. However, ICTY and ICTR can judge alleged criminals already sentenced by national courts if:

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