President Donald Trump, responding to sometimes-violent protests following the death of George Floyd at the hands of police, said he would send in the U.S. military to “quickly solve” the problems of looting and rioting if the nation’s mayors and governors did not act forcefully enough. The use of the armed forces within U.S. borders is strictly governed by federal law, however, and there would be serious questions about the legality of such a move.

1. What does the law say?

The 1878 federal law known as the Posse Comitatus Act, along with amendments and supporting regulations, generally bars the use of the active-duty U.S. military -- the Army, Navy, Air Force and Marines -- from carrying out domestic law enforcement. The law doesn’t apply to state-based National Guard units, some of which have already been deployed to help with the current unrest. Important exceptions to the law, and the ones Trump likely meant to invoke, are contained in the 1807 Insurrection Act and its modern iterations, which allow the president, without congressional approval, to employ the military for domestic use in certain circumstances.

2. Has that happened before?

Yes, many times. In the late 1800s and early 1900s, federal troops were deployed on several occasions to put down strikes. Presidents have also previously invoked the Insurrection Act to respond to civil unrest and rioting. Lyndon Johnson deployed U.S. troops or National Guard soldiers put under federal control in Detroit, Chicago and Baltimore to help quell race riots in the late 1960s. In the most recent instances of a president invoking the Insurrection Act, George H.W. Bush sent U.S. troops to the U.S. Virgin Islands in response to looting after Hurricane Hugo in 1989 and to respond to rioting in Los Angeles in 1992. It’s important to note that both Johnson and Bush acted in response to requests for federal assistance from state and territorial governors.

3. Are governors asking for help now?

In response to Trump’s June 1 comments, governors of some states that have seen rioting, including J.B. Pritzker in Illinois and Andrew Cuomo in New York, emphatically said they would not be asking the president for military assistance. (Pritzker and Cuomo are Democrats, Trump a Republican.) But Trump appears to be asserting the right to act on his own.

4. Can the president act on his own?

The Insurrection Act has been used very rarely to deploy federal troops domestically without a request from a state government, with examples mostly dating from the Civil Rights era. President Dwight Eisenhower sent Army paratroopers to help desegregate Central High School in Little Rock, Arkansas, in 1957 in opposition to the state’s governor. And President John F. Kennedy in 1962 sent troops to deal with riots over the admission of a black student to the University of Mississippi. Enforcing civil rights and other federal laws in the face of state action or inaction are circumstances under which a president could unilaterally deploy the military domestically.

5. Would the law allow Trump to act alone in the current situation?

Many legal experts believe it would. Noah Feldman, a Harvard University law professor and Bloomberg Opinion columnist, says the broad language of the Insurrection Act means Trump “might have a case” that the rioting and looting “is obstructing execution of federal law to the extent that local police and the National Guard can’t successfully stop violence on the streets.” Stephen Vladeck, a University of Texas law professor, said he believes Trump “would be within his rights -- whether we like it or not -- to use the federal military in at least some of these localities where we’ve seen multiple nights of domestic disorder and where there are genuine concerns about whether local authorities are in a position to adequately respond to and calm the threat.” Overriding governors to deploy U.S. troops to the streets of American cities would no doubt prompt serious pushback. “President Trump is not a dictator and he doesn’t have the right to unilaterally deploy U.S. military across American states,” New York Attorney General Letitia James tweeted. “We will guard the right to peaceful protest & will not hesitate to go to court to protect our constitutional rights during this time & well into the future.”

6. What steps would Trump need to take?

The Insurrection Act requires the president to issue a proclamation ordering “insurgents to disperse and retire peaceably to their abodes within a limited time.” Beyond that, he may not even need to literally deploy federal troops. In many instances in the past, presidents have simply taken over state National Guard units from governors. Eisenhower federalized the entire Arkansas National Guard in 1957.

For more articles like this, please visit us at bloomberg.com

©2020 Bloomberg L.P.