This book examines the conditions for the entry and residence in the European Union of third-country nationals and stateless persons during times of emergency, including terrorist threats, risks to health and life, and mass migration. It addresses one of Europe’s most pressing challenges: the management of irregular migration. Against the backdrop of reforms introduced by the New Pact on Migration and Asylum, the book offers a multi-perspective analysis grounded in EU law and the national legal systems of Belgium, Czechia, France, Italy, Poland, and Slovakia. It also explores the limits of state action in situations of emergency and examines how restrictions adopted in the name of state security or public order must remain consistent with the protection of fundamental rights.