This article addresses the main legal challenges facing the European Union (eu) Naval Force, eunavfor Med (‘Operation Sophia’), established in 2015, to disrupt human smuggling and trafficking activities in the Mediterranean Sea. It examines a number of legal issues that have given rise to scepticism on the viability of this type of operation, ranging from challenges under European Union law regarding mandate and oversight, to complex questions of compliance with international law. Forcible measures may be at variance with the international law of the sea, binding on the eu and its Member States alike. Even if such strictures can be avoided by a broad United Nations mandate and/or the consent of the neighbouring government(s), international refugee law and international human rights law provide limitations on the measures that Operation Sophia will be tasked with. Different avenues will be explored to ensure the Operation’s compliance with these different legal regimes.