This law school casebook examines how the vast increase in international movements of people, capital, goods, ideas and information affects politics in and beyond nation-states, the rule of law and separation of powers, and fundamental rights. It contains case excerpts from at least 40 countries in all continents, examining the assumptions, choices and trade-offs, strategies and effects of decisions from constitutional courts and human rights tribunals in different legal systems and political contexts. It discusses different theories of constitutionalism and how constitutional democracies address similar issues, in different institutional settings. The fourth edition contains two new chapters addressing respectively illiberal and populist constitutionalism and developing national and transnational constitutional treatments of climate change. In addition, this edition newly covers transgender equality rights, recent constitutional treatments of secession movements, and use of emergency powers to confront the Covid-19 pandemic.