The law of state responsibility has been affected by profound changes that have taken place in international affairs. The doctrine that used to concern mainly bilateral state relations has faced numerous challenges on different fronts. Globalization has empowered non-state actors, states have become less powerful and new issues of varying importance have emerged, some clearly demanding global attention such as climate change. Besides these external challenges, different perceptions of responsibility have appeared and gained prominence in the international arena. This fragmentation of responsibility has resulted in the coexistence of multiple responsibility regimes in international law whose relations are debated. The present study tests the law of state responsibility against the framework of functionality in order to see how well the regime and its rules meet the challenges. It is argued that normative significance must be accompanied with practical utility.