The view that international law functions independently of municipal law (hermetically), does not reflect contemporary international practice. Instead, international law in the modern era engages intensively and extensively in projects that occupy areas traditionally governed by municipal law, such as business regulation as well as the rights and duties of persons. The resulting overlap in legal dominions requires a new conceptualization of the relationship between international and municipal law. This book explores the mechanisms employed to allocate authority to international and municipal law in international disputes. Taking a broader view, this course explores the work of international bodies, domestic courts, and informal dispute resolution, including diplomacy and the use of coercive measures. It identifies the mechanisms used to manage the overlapping dominions of international and municipal law as pooling, referral, and nesting. In the final chapter, the book explores how different opportunities and ambitions for international law can affect the use of these mechanisms in particular international disputes.