President Trump has pledged to use military force if governors and mayors are unable to pacify cities across the country. As more stores, government buildings, and monuments are burned or razed, troop deployments to Washington, D.C., Minneapolis, Los Angeles, or New York are still possible. President Trump has the legal power to use the armed forces, but his authority to do so is diminished.

Article 2 (Section 2) of the U.S. Constitution assumes the President, who is named as “Commander in Chief” of the armed forces, also controls the militia (or National Guard in our context) “of the several states” when “called into the actual Service of the United States.” Though the nation lacked a large, standing military force, the Constitution distinguished between state militias and federal troops, but made it clear the President commands both entities as needed.

The Insurrection Act of 1807 carries the same distinction, but has a different purpose. The law allows the President to use both the militia and military or naval forces to quell an insurrection or address the “obstruction of the laws” of the United States or of a given state or territory. If the president has the legal authority to call forward the militia “for the purpose of suppressing such insurrection, or of causing the laws to be duly executed,” it is also, according to the act, lawful for him “to employ, for the same purposes, such part of the land or naval force of the United States, as shall be judged necessary…” The Act was amended in 2006 to give the President this same authority in other times of unrest, including natural disasters, epidemics, or other public emergencies.

Some critics have argued the Posse Comitatus Act (1878) prevents President Trump from using the military as a law enforcement entity. This is true, but it does not apply in this situation. The Act restricts the President to using the military “in cases and under circumstances expressly authorized by Congress or the Constitution.” I think the Insurrection Act provides both the case and the circumstance for the President’s ability to use the military. Posse Comitatus prevents a generalized use by the President, or when there is no insurrection or obvious obstruction of the law. President Trump seems justified in the current environment and he can credibly argue laws in many urban centers are not being “duly executed.”

There is also some confusion about the role state and local officials have in requesting or refusing troops. The Insurrection Act gives governors and legislatures the ability to request troops. It says the President “may” call into service such troops upon request. In the very next section, the act says the President’s latitude extends to “Whenever the President considers” rebellions or obstructions he “may” call into service militia as well as the armed forces. All this language suggests the President may respond to local requests but is not bound by them either positively or negatively. Presidents are not obligated to send troops when requested, and their decisions to send troops do not depend on local cooperation. This is especially relevant if state or local authorities are part of the problem.

It was precisely this kind of situation that caused President Eisenhower to invoke the Insurrection Act in 1957. Ike used elements of the 101st Airborne to defang the Arkansas National Guard (which had been called into service by Arkansas Gov. Orval Faubus) and escort African American students into Central High School. Neither Gov. Faubus nor the Arkansas legislature asked for paratroopers to be deployed, but that did not stop Eisenhower.

Eisenhower was not alone in his use of the Act. Andrew Jackson used it to quell Nat Turner’s rebellion. President Grant did the same to go after the KKK during Reconstruction. Lyndon Johnson used the military to instill order in 1967 and 1968 as Detroit and Washington D.C. were engulfed by racial tensions. George H.W. Bush used the act to assist the California National Guard in 1992 as the Rodney King riots spread across Los Angeles.

President Trump has the legal power, and the historic precedent, to use the military in this kind of situation, but his authority is shaky. Less than a third of Americans approve of Trump’s handling of the recent unrest. President Trump’s approval rating is still low. Recent polls show former Vice President Biden’s lead is growing, with a rolling average around 8 points.

President Trump has poor relationships with governors in Minnesota, California, Washington, Oregon, and New York. Though this is partisan, past presidents (like George W. Bush and Barack Obama) were sometimes able to transcend such divides, at least temporarily, during times of crisis. Any use of force now, regardless of how justified, would likely take place against the will of state and local officials.

President Trump’s approach to governance will also prove to be a hurdle. When he disagrees with critics, he claims his opponents are weak, or lack the will to succeed. There is no compromise or concession when it comes to conflict. Practically, this has left him with few political options. As Jim Geraghty describes it,

Every conflict can only be escalated. Tensions can only be ratcheted higher. Like a horned ram who likes to bash heads, the president can only charge into conflict and hope that the collision does more damage to his opponent than himself.

If President Trump decides to use the military, there is a good chance it will exacerbate tensions now and in the near future.