Under Article 17 of the Rome Statute 1998 (COMPLEMENTARITY), the ICC may exercise jurisdiction only where:

1. Article 17 Rome Statute embodies the principle of COMPLEMENTARITY — the ICC is COMPLEMENTARY to national criminal jurisdictions. 2. A case is INADMISSIBLE before the ICC where: (a) the case is being investigated or prosecuted by a State which has jurisdiction over it, unless that State is unwilling or unable genuinely to carry out the investigation or prosecution; (b) the case has been investigated by such a State and the State has decided not to prosecute, unless that decision resulted from the unwillingness or inability of the State to genuinely prosecute; (c) the person concerned has already been tried for the conduct (ne bis in idem under Article 20); (d) the case is not of sufficient gravity to justify further action by the Court. 3. Article 17(2)-(3) defines 'unwillingness' and 'inability'. 4. Hence option B is correct. _Source: UN Charter 1945 / Vienna Convention on Law of Treaties 1969 / ICJ Statute / ARSIWA 2001 — Rome Statute of the International Criminal Court 1998, Article 17_