Question

what is complementarity law

Answer 1

The complementarity principle on which the International Criminal Court (ICC) is based entails that the ICC can only investigate and prosecute core international crimes when national jurisdictions are unable or unwilling to do so genuinely. ... It was created as an admissibility principle of the ICC.

Answer 2

Complementarity governs the relationship between the ICC and national legal orders. Article 17 of the Rome Statute allows the ICC to step in and exercise jurisdiction where states are unable or unwilling genuinely to investigate or prosecute, without replacing judicial systems that function properly.