This article analyzes the international law obligations that arise in relation to nationally determined contributions (NDCs). It argues that distinct and concurrent obligations arise from two separate sources. On the one hand, treaty obligations arise under the Paris Agreement, which imposes an obligation of conduct on parties: they must take adequate measures towards the realization of the mitigation targets contained in their NDCs. On the other hand, communications such as NDCs may constitute unilateral declarations that also create legal obligations. These unilateral declarations impose obligations of various types, which may extend beyond mitigation. For example, they may specify measures of implementation or demand the achievement of a particular result. The potential ‘double-bindingness’ of NDCs should be a central consideration in the interpretation of international law obligations regarding climate change.
