The United States military has significantly expanded its role along the southern border, establishing sweeping new enforcement zones where troops are authorized to detain individuals entering the country illegally. Under a continuing national emergency order declared by former President Donald Trump, the Department of Defense has posted thousands of orange no-entry signs across parts of New Mexico and western Texas. These signs mark “restricted areas” now under military control, creating a precedent-setting shift in the military’s involvement in civilian law enforcement along the border.

The new military buffer zones stretch across 230 miles from Fort Hancock, Texas, to western New Mexico, with an additional 250-mile zone recently implemented in Texas’ Rio Grande Valley. Another zone is planned near Yuma, Arizona. Collectively, these areas now account for nearly one-third of the entire U.S.-Mexico border. Oversight is divided between Army commands at Fort Bliss in Texas and Fort Huachuca in Arizona. According to the Pentagon, the zones are intended to close enforcement gaps in isolated desert regions and to combat human smuggling networks and drug trafficking activity that continue to exploit weaknesses in the current system.

This expanded military presence is being patrolled by at least 7,600 active-duty troops, marking the largest peacetime deployment of military forces for immigration enforcement in U.S. history. These deployments allow troops to detain migrants and oversee stretches of the border previously managed exclusively by Customs and Border Protection. Officials argue that the move strengthens national security and provides “teeth” to long-standing surveillance operations. However, legal experts and civil liberties groups have raised alarms over what they view as an erosion of the Posse Comitatus Act, the 1878 law prohibiting the military from carrying out civilian law enforcement functions without congressional approval.

Federal courts are already hearing legal challenges to the militarized zones. Public defenders have argued that the Department of Defense has unilaterally designated public lands for military enforcement without proper legislative authority. One ongoing case involves a Mexican national charged with trespassing through military territory. While some migrants have had their trespassing charges dismissed, others have been convicted, particularly those who returned to military zones after being warned.

More than 1,400 migrants have been charged with trespassing on these military-controlled lands, facing potential prison sentences of up to 18 months for a first offense. These charges are in addition to standard illegal entry violations, which carry penalties of up to six months. Most of those convicted are ultimately transferred to immigration authorities for likely deportation. In one court proceeding in Las Cruces, New Mexico, a 29-year-old Guatemalan woman was sentenced to two weeks in jail after pleading guilty to illegal entry. Her trespassing charges were dropped due to lack of evidence. Her public defender stated she had a sixth-grade education and sold pottery in her home country.

The introduction of military zones has drawn mixed reactions from local residents. In Luna County, New Mexico, where vast stretches of the new zone now lie, some farmers and ranchers support the increased security presence. James Johnson, a fourth-generation farmer, called the deployments a necessary step in combating border-related crime. Others, including hikers, hunters, and local officials, have expressed concern about being blocked from accessing public lands. Luna County Commissioner Ray Trejo said he worries about accidental confrontations, especially for armed civilians using the land for recreation. Trejo, a former public school teacher, also raised ethical concerns over punishing migrant workers who unknowingly cross into military zones while seeking employment.

The Army has said it is negotiating access rights for hunting and recreation and will honor existing grazing and mining permits. However, many civil liberties advocates argue the current model represents a dangerous precedent. Rebecca Sheff, an attorney with the American Civil Liberties Union, warned that the zones are likely being used as a test case for more aggressive and permanent militarization of the southern border. She called the expansion a “vehicle” to normalize military presence in domestic immigration enforcement, which she said raises serious constitutional concerns.

Despite the heightened enforcement, U.S. Customs and Border Protection reports that arrests along the southern border have dropped to the lowest levels in six decades. In June, arrests declined by 30% compared to the previous month. On June 28, just 137 individuals were apprehended at the border, a sharp contrast to peaks in late 2023 when daily arrests exceeded 10,000.

In Columbus, New Mexico, where one of the militarized zones surrounds a small border village, the presence of military vehicles has been minimal, according to Mayor Philip Skinner. The town, home to 1,450 residents, has long served as a cross-border hub where children with U.S. citizenship regularly travel from Mexico to attend public schools. Skinner said he’s seen little disruption so far and suggested that national politics have not heavily influenced local sentiment.

Rancher Russell Johnson, whose property straddles the border on land leased from the Bureau of Land Management, supports the military deployment and recalled numerous encounters with smugglers and criminal activity on his land. He described scenes of high-speed vehicle chases and the discovery of bodies by Border Patrol agents. Johnson said military vehicles had recently been stationed near a gap in the border wall but noted that their presence has decreased in recent weeks.

As federal courts consider the legality of the new zones, the Department of Justice is pushing forward with prosecutions. In June, two individuals were convicted of trespassing after re-entering military zones. U.S. Attorney Ryan Ellison stated during a press conference that the government would continue to pursue such cases and ensure violators are held accountable.