A series of prominent mass shootings in the United States (US) has prompted renewed interest in revising gun policy. One proposal that has gained political traction is raising the minimum age for purchase and possession of guns to 21. While some commentators have suggested that the public mood may be shifting on gun policy, proposals to raise the minimum age have nevertheless provoked controversy. In this manuscript, we examine the ethical acceptability of raising the minimum age of purchase and possession of guns to 21. First, we examine the nature of the rights claim at issue. Second, we examine liberty-based objections to minimum age laws, and offer counter-arguments to these claims. Then, we examine the nature of the harm to be prevented via minimum age laws. We conclude that gun ownership is an important right, but one that nevertheless is ethical to regulate. We argue that liberty-based objections to minimum age laws are not as strong as critics of these laws claim. While we acknowledge the data limitations on assessing their likely success in reducing gun-related harms, we argue that minimum age laws are an ethically permissible policy strategy. We conclude with several recommendations for further research and policy responses to addressing the toll of gun-related morbidity and mortality.