Can a State, without going to the Security Council, claim in these circumstances the right to act, in anticipatory self-defence, not just pre-emptively (against an imminent or proximate threat) but preventively (against a non-imminent or non-proximate one)? Those who say “yes” argue that the potential harm from some threats (e.g., terrorists armed with a nuclear weapon) is so great that one simply cannot risk waiting until they become imminent, and that less harm may be done (e.g., avoiding a nuclear exchange or radioactive fallout from a reactor destruction) by acting earlier.