Although Donald Trump's foreign policy behavior is often characterized as erratic and unpredictable, he was remarkably consistent in his hostility toward international agreements. The president withdrew or threatened to withdraw the United States from several agreements and consistently characterized agreements as `horrible deals¿ that `cheat¿ his country. This article explores why Trump exhibited such consistent disdain for international agreements. To address this question, it develops propositions that draw a causal link between a leader¿s personality traits and their willingness to challenge constraints: a leader with a relatively high belief in their ability to control events is more likely to challenge constraints than a leader with a lower belief in their ability to control events; moreover, a leader with a relatively high level of distrust of others is more likely to challenge constraints than a leader with a lower level of distrust of others. The article then conducts a plausibility test of these propositions in the context of Trump¿s decisions to withdraw from agreements in three significant policy areas: trade (the Trans-Pacific Partnership), environmental stewardship (the Paris Agreement on climate change), and nuclear proliferation (the Iran nuclear deal).