The doctrine of PROPORTIONALITY in jus ad bellum (right to wage war) requires that:

1. The PROPORTIONALITY principle in jus ad bellum (right to use force) requires that self-defence under Article 51 UN Charter must be proportionate to the armed attack and necessary to repel it. 2. The ICJ in Military and Paramilitary Activities in and against Nicaragua, 1986 ICJ Rep 14, para. 176: 'self-defence would warrant only measures which are proportional to the armed attack and necessary to respond to it.' 3. The ICJ in Oil Platforms (Iran v. USA), 2003 ICJ Rep 161, paras. 73-77, applied the test. 4. Distinct from proportionality in jus in bello (IHL — Article 51(5)(b) AP I — civilian harm proportional to military advantage). 5. Hence option B is correct. _Source: UN Charter 1945 / Vienna Convention on Law of Treaties 1969 / Geneva Conventions 1949 / ICJ Statute / UDHR ICCPR ICESCR — Customary international law; Nicaragua v. USA, 1986 ICJ Rep 14, para. 176; Oil Platforms (Iran v USA), 2003 ICJ Rep 161_