Jorge E. Viñuales
This chapter addresses the challenges posed by the practice of international investment law to the conventional theory of the sources of international law. After a brief overview of the main ‘sources’ of ‘international investment law’, the chapter examines three challenges to this basic understanding, which arise from the need to account for the domestic laws governing different aspects of foreign investment transactions, the detailed jurisprudential norms generated by investment tribunals to specify broadly formulated norms, and the norms of general international law expressing the sovereignty of the State. For each category of norms, the chapter selects several problems that put the most widely accepted understanding of the sources of international law to test. It then explains why the problems examined have potentially important practical implications. The chapter concludes with some observations on the interactions between practice and the theory of the sources of international law.