Yale Law School
The military is currently prohibited by federal statute from participating in domestic law enforcement. The Posse Comitatus Act of 1878 ("PCA") establishes criminal penalties for people who willfully use members of the Army or the Air Force to execute the laws. Although a product of the Reconstruction Era, this law reflects a strong American tradition against the domestic use of the military that stretches back before the founding of the nation.
Sean J. Kealy,
Reexamining the Posse Comitatus Act: Toward a Right to Civil Law Enforcement
Yale Law & Policy Review
Available at: https://scholarship.law.bu.edu/faculty_scholarship/2095