On May 8, 2018, President Trump withdrew the US from the Joint Comprehensive Plan of Action (JCPOA). Since the JCPOA is endorsed by a United Nations Security Council Resolution and supported by the international community, Trump has had to justify this controversial decision. Based on data extracted from Trump’s Twitter account and taking advantage of Theo van Leeuwen’s (2008) discursive construction of the legitimation model, this article addresses the following question: How has Donald Trump attempted to delegitimize the JCPOA?