In chapter 4, I examine the debates of 1965–66 over Australia’s participation in the Vietnam War. In 1965–66, the UN Charter regulated the use of force by states but the success of international legal arguments in the public debates did not depend on the ability of the speaker to characterise an argument as a ‘legal’ one. Successful use of international legal language in the 1965–66 debates depended on the ability of the speaker to cast international law as something more than merely law – as either a standard of morality or a manifestation of an alliance. The legality or illegality of Australia’s actions was not enough, on its own, to provide a persuasive justification for war in 1965–66.