This article explores the relationship between mutual trust and fundamental rights. It argues that mutual trust is a systemic principle of EU law only when activated by the free movement provisions, and even in that case it is relative in that it can be limited by fundamental rights. However, when there is no free movement, mutual trust needs to be activated by secondary legislation, and it is an administrative principle which requires mutual recognition only if that is provided in secondary legislation. The article then seeks to apply this categorization to the case law on the European Arrest Warrant and instruments adopted within the Common European Asylum System.