This study examines the historical development and institutional logic of counterintelligence support to immigration governance in the United States. It traces the evolution of immigration control from early twentieth-century wartime security measures to the formation of a complex, legally constrained counterintelligence framework integrated into federal immigration policy. The analysis demonstrates how immigration gradually became a security-sensitive domain shaped by statutory law, constitutional limitations, and interagency coordination. Special attention is given to the role of internal security legislation, alien registration systems, ideological screening mechanisms, and the institutional consolidation of counterintelligence functions across different historical periods, including World War I, World War II, the Cold War, and the post–Cold War era. The study further explores the adaptation of this framework to large-scale migration flows, asylum regulation, and emerging transnational threats. Rather than focusing on episodic enforcement or individual actors, the work emphasizes institutional design, legal continuity, and governance logic. It argues that the effectiveness of U.S. counterintelligence in the immigration domain derives from its capacity to balance preventive security objectives with constitutional guarantees, procedural restraint, and long-term institutional adaptability.