This chapter charts the development of the law that applies when a state is requested by another state to extradite an individual in actual or potential death penalty cases. It is generally accepted now that international law demands abolitionist states to seek and obtain assurances that the death penalty will not be imposed or carried out, before extraditing a person. Similarly, retentionist states must seek assurances that the death penalty will only be applied in line with standards of international human rights law before extraditing a person. While these rules are generally agreed upon, the principles that underpin these rules have received little attention. These principles warrant exploration, though, since they have implications beyond the field of extradition. Two such principles are identified: (i) the jurisdictional principle, which prohibits states from subjecting individuals in their jurisdiction to punishments that have been outlawed; and (ii) the principle of non-complicity, which prohibits states from being complicit in punishments that it has outlawed. With this in mind, it is argued that the legal framework in extradition cases should be extended to mutual legal assistance and other cases of complicity with capital punishment, such as the provision of intelligence, resources and evidence in actual or potential death penalty cases.