Which act prohibits military forces from directly engaging in law enforcement activities?

The Posse Comitatus Act specifically prohibits the use of the U.S. military in a direct capacity to enforce domestic laws. This act was established in 1878 and emphasizes the principle of civil control over the military, ensuring that military personnel do not engage in law enforcement activities on U.S. soil unless explicitly authorized by law or constitutional provision. This restriction aims to maintain the separation between civilian law enforcement and military operations, preserving democratic processes and civil liberties.

The other options do not serve the same function as the Posse Comitatus Act. The Military Cooperation Act focuses on international military training and cooperation rather than domestic law enforcement. The National Defense Authorization Act primarily governs military funding and policy decisions related to defense. The Homeland Security Act addresses issues related to securing the nation against terrorism and managing domestic security organizations but does not impose the same restrictions on military involvement in law enforcement as the Posse Comitatus Act. Thus, the Posse Comitatus Act stands out as the law specifically designed to prevent military forces from engaging directly in law enforcement activities.