Could President Trump order troops onto the streets of a major American city over the objections of local and state officials?
Trump threatened to do so Monday, saying that if governors and local officials failed to end civil unrest, he would deploy the military “to do the job for them.”
Normally, military troops are forbidden by law to be involved in law enforcement within the U.S. But that prohibition has some exceptions. The main one involves the Insurrection Act, first passed early in the country's history, under which a president can order active-duty troops to be used for domestic law enforcement if doing so is needed to suppress an insurrection or civil disturbance.
In most cases, the law allows the president to do that only if he is asked to do so by a state governor or legislature.
In 1992, for example, when the acquittal of police officers on charges of beating motorist Rodney King sparked rioting in Los Angeles, California National Guard units were federalized at the request of then-Gov. Pete Wilson to quell the riots. That was the last time the Insurrection Act was invoked.
If a state actively opposes the use of federal troops, as several governors indicated on Monday that they would, the law might still allow it in certain cases, according to a 2018 report by the Congressional Research Service.
One of the main exceptions is when a state is violating people's civil rights. In 1957, for example, President Eisenhower ordered the 101st Airborne Division into Little Rock, Ark., and federalized the entire Arkansas National Guard in order to enforce a court order permitting nine black students to attend a previously all-white high school.
Presidents Kennedy and Johnson later used the same legal authority to enforce court orders for desegregation in several Southern states.
Some of Trump's rhetoric has suggested his administration's lawyers might try to justify deploying troops by arguing that rioters are depriving citizens of their civil rights. An argument of that sort would be unprecedented, but Trump has often shown a willingness to flout precedent.
Sending troops to quell riots without a request from a state is not automatically allowed under the law. In 2007, Congress loosened restrictions on deployments, giving a president the power to employ federal troops to “restore public order and enforce the laws of the United States” without a request from the governor or legislature of the state involved. But the provision was repealed a year later because of objections by states that it gave the federal government too much power.