President Donald Trump on Friday issued a memorandum authorizing the U.S. military to take control of a strip of federal land along the southern border to curb illegal immigration and drug trafficking.

The cabinet members should “take all appropriate actions” to facilitate Department of Defense jurisdiction over federal lands “reasonably necessary” for military operations outlined in the memo, the president said.

Those operations include the construction of border barriers and the deployment of detection and monitoring systems. Hegseth is tasked with determining which military activities are “reasonably necessary and appropriate to accomplish the mission assigned.”

The memo does not apply to Native American reservations but does extend to the Roosevelt Reservation, a 60-foot wide corridor that runs along the U.S.-Mexico border in California, Arizona, and New Mexico.

Trump also authorized Hegseth to treat areas where troops are deployed as military installations, granting him the authority to “protect and maintain” those zones and restrict access as necessary.

At any time, Trump noted, Hegseth may expand operations to additional federal lands along the southern border, in coordination with the secretary of homeland security, the assistant to the president for homeland security, and other relevant agencies.

The initial phase of the operation is set to be evaluated within 45 days, according to the memo.

The move comes as Trump weighs invoking the Insurrection Act of 1807, an early Republic-era law that authorizes the deployment of active-duty military to enforce federal law when state authorities are unable or unwilling to do so.

The departments of Defense and Homeland Security have been asked to submit recommendations on the matter by April 20 as part of the administration’s broader plan to carry out its promised mass deportation of illegal immigrants.