This chapter provides an overview of the different approaches taken by the international community to address liability from environmental harm and how these approaches respond to the unique legal and practical issues associated with areas beyond national jurisdiction. Since liability rules that affect the commons environment exist in both international and national legal systems, the discussion begins with an examination of state responsibility and unharmonized domestic liability, before discussing various approaches to harmonizing civil liability rules through treaties. The discussion of approaches to liability is framed by consideration of the various purposes that liability rules and processes serve in international environmental law.