This chapter describes some international law that is applicable to climate engineering, with a focus on international environmental law. It closes with a brief synthesis and some recommendations for future developments. First, though, it introduces international law and suggests why climate engineering is such a challenge for international environmental law and its scholars. International law is a collection of authoritative rules governing countries' actions, especially those that may impact other countries. That is, sovereign states are its subjects. With limited exceptions, international law governs neither the actions of individual persons nor those of national governments that have only domestic impacts. International environmental law is the logical starting point for considering how international law may be able to prevent and resolve disputes arising from climate engineering. Climate engineering presents difficulties for international environmental law and its scholars. To some degree, this is due to its novelty: climate engineering proposals have been seriously discussed.