Which act restricts the U.S. military from civilian police actions?

• A. Insurrection Act
• B. Posse Comitatus Act (1878)
• C. Patriot Act
• D. National Security Act

Answer: (B)

The legal boundary between civilian police powers and the military on U.S. soil is what this question targets. The Posse Comitatus Act of 1878 prohibits federal military personnel from enforcing civilian laws domestically, except in cases explicitly authorized by the Constitution or Congress. This restriction is exactly what keeps the military from acting as a civilian police force in ordinary domestic matters, making it the correct choice. The Insurrection Act provides limited exceptions that let the president deploy troops to deal with insurrection or certain emergencies, but it does not establish the general restriction itself. The Patriot Act expands civilian law enforcement powers, not military enforcement constraints, and the National Security Act reorganized national security and intelligence structures without addressing domestic police power.