CUSTOMARY INTERNATIONAL LAW under Article 38(1)(b) ICJ Statute has two constitutive elements:

1. Customary international law requires two constitutive elements: (1) GENERAL STATE PRACTICE — constant, uniform, of sufficient duration, by States generally; and (2) OPINIO JURIS SIVE NECESSITATIS — belief by States that the practice is legally required (not just usage or comity). 2. The ICJ in North Sea Continental Shelf Cases (Germany v Denmark and Netherlands), 1969 ICJ Rep 3, laid down the test for opinio juris. 3. The PCIJ in Lotus (France v Turkey), 1927 PCIJ Ser A No 10, applied the practice test. 4. The Nicaragua case (1986) used multiple sources to establish opinio juris. 5. Hence option B is correct. _Source: UN Charter 1945 / Vienna Convention on Law of Treaties 1969 / ICJ Statute / ARSIWA 2001 — ICJ Statute Article 38(1)(b); North Sea Continental Shelf Cases (1969); Lotus Case (PCIJ 1927)_