In The Law of Peoples, John Rawls defends the claim that ‘decent’ societies (non-liberal, non-democratic constitutional republics) deserve full and good standing in the international community. His defense of decent societies consists of two main arguments. First, he argues that the basic human right to political participation does not imply a right to democratic political institutions. This argument has been thoroughly discussed by commentators. Second, he argues that decent societies, if admitted to the international community, would pose no special threat to the stability of that community. This argument has largely been ignored. My aim in this article is to analyze this second argument, which I call the ‘peace argument’.