Self-defence (Article 51): "Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs... until the Security Council has taken the measures necessary..."
• The Caroline criteria (1837 — the pre-Charter classic, still the measure): necessity "instant, overwhelming, leaving no choice of means, and no moment for deliberation" + proportionality (the response's scale to the attack);
• The Charter-era limits: armed attack's occurrence (the Nicaragua threshold: the "most grave" forms — excluding mere frontier incidents' armed attack status); immediacy and proportionality; reporting to the Council (Article 51's clause); the Council's displacement role;
• The contested extensions: anticipatory self-defence (against imminent attack — the Caroline's own case) vs. pre-emptive (against distant threats — the doctrine's American misuse debate); collective self-defence (the victim-state's request requirement — Nicaragua; the Gulf War coalition's architecture); 9/11's aftermath — self-defence against non- state actors (Afghanistan 2001) and the "unwilling or unable" doctrine's rise — the era's hardest controversy;
• Nepal's note: the state's own history as the system's consumer (the 1815 Sugauli-era world) and citizen (Charter-era peacekeeping — IRD Unit 4's record), and the perennial line: Nepal's diplomacy for the Charter's strict reading.
Collective security (Chapter VII): the Council's graduated machinery — Article 39 (the breach/ threat/aggression determination); Article 41 (non-force measures: sanctions — the era's sanctions regimes; embargoes — Unit 8's compulsive cousins); Article 42 (military enforcement — authorized coalitions); the Military Staff Committee's sleep; the veto's shadow (the P5's paralysis cases — Syria; the Ukraine 2022 general assembly's Uniting for Peace revival); the General Assembly's subsidiary roles (Uniting for Peace 1950; recommendations and the "responsibility to protect" debate of IRD Unit 3); regional arrangements (Chapter VIII) — Unit 4's enforcement questions.