This article is part of a special issue of the Cambridge Journal of International & Comparative Law addressing the concept of the fundamental rights of states in international law. The article will first consider this theme from a legal theoretical perspective. It will conclude that fundamental rights of states exist in international law as autonomous juridical principles. The article will then proceed to discuss one such asserted fundamental right of states: the right to peaceful nuclear energy, as codified in the 1968 Nuclear Nonproliferation Treaty. It will argue that the right to peaceful nuclear energy is indeed a fundamental right of states, and that it has juridical substance, and carries juridical implications, as a rule of law on par with other rules of the jus dispositivum.