The memo, signed by Chief of Staff John Kelly late Tuesday, authorizes military personnel to protect border agents using “reasonably necessary” activities, and included examples such as crowd control, searches, temporary detention, and lethal force if necessary, the report said.

The memo stated that the authorization was necessary because “credible evidence and intelligence” indicate that the thousands of migrants near Tijuana, Mexico “may prompt incidents of violence and disorder,” The Military Times reports.

Legal experts told The Military Times that the authorization may violate the 1878 Posse Comitatus Act, which limits the U.S. military from conducting law enforcement duties on U.S. soil and argued that the move could fundamentally change the military and how it’s used.

Ever since a caravan of thousands of migrants began traveling north to the United States from Honduras, El Salvador, and Guatamala, President Donald Trump has called the act an invasion and has taken steps to stop them from entering. He considered closing the border entirely, attempted to limit assylum claims, and deployed more than 5,000 troops to the border and has vowed to triple that number.