. . . but his notion of bringing home troops from Iran and Afghanistan, his same old isolationist song and dance, as a means of enforcing the borders of the U.S. is actually a violation of federal law.
The Posse Comitatus Act is a United States federal law (18 U.S.C. § 1385) passed on June 18, 1878, after the end of Reconstruction, with the intention (in concert with the Insurrection Act of 1807) of substantially limiting the powers of the federal government to use the military for law enforcement. The Act prohibits members of the Army from exercising nominally state law enforcement, police, or peace officer powers that maintain "law and order" on non-federal property (states and their counties and municipal divisions) within the United States.