Proliferation of major conventional weapons (MCW) in larger numbers, at greater levels of sophistication, and to more actors is at best a waste of valuable resources and at worst fuel for more and bloodier conflicts. Given a track record of violence, repression, and corruption, norms against exporting weapons to active conflicts and human rights abusers, as well as norms in favor of transparency in weapons transfers, have grown more salient in recent years. Yet international efforts such as the UN Conventional Arms Trade Treaty show little promise for mitigating these ills. This article finds an alternate route toward moderating global arms transfers. It shows, with supporting data, how the United States, pursuing its own political interests, leverages its massive market power to slow the proliferation of dangerous technology, reduce resources spent in the developing world on weapons, stymie the deadweight losses of corruption in the arms industry, and lower the rewards for human rights abusers.