This book focuses on sovereign states of the Global South, offering a systematic analysis of how these countries design voting rules within regional international organizations. It introduces the concept of travel restriction measures and examines them in conjunction with the national and social interests of Global South countries, with the aim of identifying pathways toward mutually beneficial cooperation within a shared community of interests. The book also places strong emphasis on collaborative approaches to cultural heritage protection among Global South countries, interpreting the legal and institutional mechanisms that support cross-border cooperation in this field. In light of the persistent tension between environmental protection and economic growth faced by many Global South countries, the book further foregrounds sustainable development as a central theme. Several chapters examine key environmental governance issues—including climate change, environmental provisions in free trade agreements, and marine plastic pollution—from the perspective of Third World Approaches to International Law (TWAIL), engaging critically with questions of environmental justice in the governance of global environmental threats. Characterized by policy analysis, professional interpretation of legal provisions, and a case-oriented research approach, this book aims both to popularize policy and legal theory for broader audiences and to provide valuable reference material for scholars and policymakers in Global South countries. Overall, it addresses the challenges confronting Global South states in an era marked by rapid technological advancement, intensifying environmental risks, and growing demands for sustainable development.