Nuclear and other radioactive materials are being trafficked outside the realm of legality. These materials are likely to be used in terrorist attacks that could inflict, given the extremely perilous nature of such substances, an enormous amount of casualties and many unforeseen consequences. This fact raises crucial issues that require a precise examination of the wide variety of international legal instruments that could potentially be invoked to curb this threat. Given the shift from traditional nuclear energy markets towards new frontiers, it is indeed crucial to better investigate this phenomenon and the role that can be played by international law in the fight against illicit trafficking in nuclear materials, examining how the law views the different actors of the nuclear black market, in particular non-State actors, and which mechanisms have been set up so far in order to prevent and tackle this menace.