SUMMARY

The prohibition of the threat or use of force in article 2(4) of the UN Charter applies to nuclear weapons as it does to conventional uses of force. Likewise, an armed attack giving rise to the right to use force in self defence might take the form of a nuclear strike. It is the scale and effects of the nuclear strike that will determine its classification as a use of force and armed attack. The principle of distinction and linked rules of the law of targeting also apply to nuclear operations. The legal position differs as between States that are or are not party to API and as between such States party that did or did not make nuclear statements when ratifying the treaty. For all States, there is an obligation to take constant care in nuclear operations to spare civilians and civilian objects. More detailed precautionary rules apply to all States with certain additional rules only applying to States that are party to API and that made no nuclear statement. States adopt numerous measures to disseminate this body of law and international engagement seems to be the best approach for promoting international compliance.

In this essay, Bill Boothby observes: “For all States, there is an obligation to take constant care in nuclear operations to spare civilians and civilian objects. More detailed precautionary rules apply to all States with certain additional rules only applying to States that are party to API and that made no nuclear statement. States adopt numerous measures to disseminate this body of law. International engagement seems to be the best approach for promoting international compliance.”

This paper is accompanied by a Fourth Leg podcast: Are All Legal Bets Off