President Donald Trump’s latest memorandum has stirred legal and constitutional debate across New Mexico and beyond. On Friday, Trump announced that a 60-foot-wide strip of federally owned land along the U.S.-Mexico border — known as the Roosevelt Reservation — would be placed under temporary control of the U.S. military. This corridor stretches from California to New Mexico, encompassing the entirety of New Mexico’s southern border.The directive, issued via presidential memo, gives the Department of Defense authority over the strip of land for 45 days while it assesses the feasibility of a military presence. While the Trump administration says the move is necessary to combat a "variety of threats" at the southern border, critics and legal experts argue it may conflict with longstanding federal law.Legal Concerns: Posse Comitatus ActAt the heart of the legal debate is the Posse Comitatus Act, a Reconstruction-era law that prohibits the use of federal military personnel to enforce domestic laws unless expressly authorized by Congress. The law is designed to uphold civilian control over domestic law enforcement and prevent the military from acting as a national police force.“This is an old law that’s been on the books since the 19th century, but it applies to the present day,” said KOAT legal expert John Day. “It bars federal troops from conducting domestic law enforcement, and any attempt to expand their role at the border must navigate that carefully.”According to a report from the Associated Press, the administration appears to be attempting an end-run around the law by treating the Roosevelt Reservation as a military installation. Trespassing on military installations is illegal.What Will Troops Actually Do?More than 7,000 active-duty troops, including a Stryker team, are already stationed at the border under Trump's national emergency declaration. Thus far, they have only provided logistical support to U.S. Customs and Border Protection (CBP), such as surveillance and intelligence gathering. They have not had the power to make arrests.However, the latest memo suggests a potential escalation in their role — a move that remains legally murky.“Until there’s a clearer picture, we don’t really know exactly what they’re going to do,” said Day. “Are they engaged in law enforcement duties? Are they assisting CBP in a support role? That will determine whether this violates the law or not.”Day added that the key legal question will be whether troops are merely supporting CBP or directly engaging in enforcement activities, which would cross into prohibited territory under the Posse Comitatus Act. The announcement comes despite CBP data showing a significant decrease in illegal crossings in all three states the Roosevelt Reservation touches: California, Arizona, and New Mexico. The administration, however, insists that national security risks persist along the border. The presidential memo requires the Secretary of Defense to reassess the use of military personnel on the Roosevelt Reservation after 45 days. Whether the military will assume a larger enforcement role — and whether that role withstands legal scrutiny — remains to be seen.For now, the military's presence along New Mexico's border will be closely watched by legal experts, lawmakers, and civil rights advocates.