Abstract
International law often develops incrementally over a long period of time through both the creation of new law and the interpretation (and reinterpretation) of existing law. The law on the protection of forcibly displaced persons provides an apposite case study of incrementalism in international lawmaking, with international efforts in this area going back to the 1920s, when the Council of the League of Nations created a refugee commissioner post to address the needs of persons displaced from Russia. Two types of incrementalisms may be identified in the development of this area of international law: (1) horizontal incrementalism, in which a norm initially established with limited applicability is subsequently expanded; and (2) vertical incrementalism, in which a norm initially created in a weak or legally soft manner is subsequently strengthened or hardened. A close examination of the law on the protection of forcibly displaced persons and its development suggests that such incremental lawmaking may be explained by the extent to which governmental political interests and humanitarian needs align, conflict, or are compatible with one another. Given that skillful advocacy and consensus-building appear essential in successful incremental expansion of law, analyses of incremental international lawmaking may empower advocates seeking to develop international law for humanitarian and other causes.