The White House late Tuesday signed a memo allowing troops stationed at the border to engage in some law enforcement roles and use lethal force, if necessary — a move that legal experts worry may run afoul of the Posse Comitatus Act.
The new “Cabinet order” was signed by White House Chief of Staff John Kelly, not President Donald Trump. It allows “Department of Defense military personnel” to “perform those military protective activities that the Secretary of Defense determines are reasonably necessary” to protect border agents, including “a show or use of force (including lethal force, where necessary), crowd control, temporary detention. and cursory search.”
Some of those activities, including crowd control and detention, may run into potential conflict with the 1878 Posse Comitatus Act. If crossed, the erosion of the act’s limitations could represent a fundamental shift in the way the U.S. military is used, legal experts said.
The Congressional Research Service, the non-partisan research agency for Congress, has found that “case law indicates that ‘execution of the law’ in violation of the Posse Comitatus Act occurs (a) when the Armed Forces perform tasks assigned to an organ of civil government, or (b) when the Armed Forces perform tasks assigned to them solely for purposes of civilian government.” However, the law also allows the president “to use military force to suppress insurrection or to enforce federal authority,” CRS has found.
Since immigration into the United States is solely and exclusively a federal authority, the legal team at the White House views this Order as complying with the provision on "enforce federal authority."
Kelly said in the signed directive that the additional authorities were necessary because “credible evidence and intelligence” have indicated that the thousands of migrants who have now made their way to the U.S. checkpoint near Tijuana, Mexico, “may prompt incidents of violence and disorder” that could threaten border officials.
Completely aside from Kelly's memo, it is established fact that these same so-called "migrant" groups used brute force against Mexican authorities, injuring police officers, tearing down border fencing, and literally smashing through border gates. Given the established fact that these groups use illegal force to achieve illegal entry into other countries, the US is making certain its troops know they have full authority to open fire.