Legal expert lays out how Trump’s military powers can — and can’t — be used during a period of civil unrest

As cities all over the United States continue to be rocked by civil unrest following the May 25 killing of George Floyd in Minneapolis, President Donald Trump has threatened to “deploy the United States military” in the streets of U.S. cities — an assertion that has been condemned as authoritarian by many observers, including historian Jon Meacham and Sen. Kamala Harris of California. But what powers does Trump actually have when it comes to the use of force? Mark Nevitt, a former U.S. Navy commander who taught at the University of Pennsylvania Law School in Philadelphia, explained the limits and extent of his authority in an article for Just Security, delving into the specifics of the Posse Comitatus Act of 1878 as well as the Insurrection Act of 1807.

During a Monday night appearance on MSNBC, Harris (a former prosecutor) said of Trump’s rhetoric, “These are not the words of a president. They are the words of a dictator.” And the following morning, Meacham appeared on MSNBC’s “Morning Joe” and told host Mika Brzezinski that Trump is “drawing on the vernacular of authoritarianism” and “verging towards the ways and means of dictatorial power.”

Those are troubling words coming from an ex-prosecutor turned U.S. senator and a presidential historian. Nevitt, analyzing Trump’s rhetoric in Just Security, explains that two questions need to be asked. The first is “Under what conditions can the president order the military to respond to Minneapolis?,” and the second is, “What are the military’s rules for the use of force — i.e., does looting justify shooting?”

Nevitt notes that Trump is “subject to certain, critical legal restrictions under both the Posse Comitatus Act and the Insurrection Act. The president is, of course, the commander-in-chief of the (U.S.) Armed Forces, but he lacks the authority to use the military in any manner that he pleases. That authority is constrained by Congress and the courts.”

Nevitt goes on to explain that the Posse Comitatus Act has “limited the president’s ability to use the federal (Title 10) military in domestic law enforcement operations such as searches, seizures and arrests. A criminal statute, the Posse Comitatus Act makes it unlawful for the Army or Air Force to ‘execute the laws…. except in cases and under circumstances expressly authorized by the Constitution or Act of Congress.’ So, the president cannot simply call in federal military forces or nationalize the Minnesota National Guard to quell the civil disturbance in Minneapolis without pointing to a Posse Comitatus Act exception.”

During civil unrest of the past, the National Guard was used in U.S. cities to restore order — and the National Guard is being used in U.S. cities during the current unrest. For example, the Pennsylvania National Guard, under Democratic Gov. Tom Wolf, is now in the streets of Philadelphia in response to all the unrest in the East Coast city. But that is way different from using federal U.S. Army troops on the streets of U.S. cities, which is what Trump has threated to do.

The Insurrection Act, according to Nevitt, is an exception to the Posse Comitatus Act.

“The Insurrection Act is, by far, the Posse Comitatus Act’s most important exception,” Nevitt explains. “This is the legal key that unlocks the door to use federal military forces — whether through federalizing the National Guard or calling in ‘Title 10 forces’ to quell civil unrest.”

Nevitt looks back on the Los Angeles Riots of 1992 and the response of Republican Pete Wilson, California’s governor at the time.

“In requesting federal troops to patrol Los Angeles,” Nevitt notes, “Wilson specified that the California National Guard lacked the ability to quell the domestic disturbance. Shortly thereafter, (President George H.W.) Bush issued an executive order, which authorized the defense secretary to federalize the California National Guard and deploy active-duty Army and Marine personnel from bases in California to the scenes of the riots.”

The Insurrection Act was passed 213 years ago, and according to Nevitt, it has seldom been used.

“In sum, invoking the Insurrection Act remains a rare occurrence in U.S. history, used in the most extraordinary circumstances, such as the complete disregard for enforcing federal civil rights laws or massive unrest in the nation’s second largest city,” Nevitt writes. “Despite the Insurrection Act’s invocation in Los Angeles, it has not been used in 28 years.”