The law against war appears to be dead. Russia’s attempt to conquer Ukraine in 2022 is the most serious breach of the prohibition on the use of force since it was codified in the United Nations Charter in 1945. Violations in the Middle East, Africa, and elsewhere are plain. Under the theory of legal positivism, such widespread and serious breaches can lead to the disappearance of once viable law. The prohibition on force, however, is no mere positive law rule. It is a peremptory norm of nat...