As Harris, Trump make final election pitch, can the U.S. military be deployed?

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In this highly polarizing and deeply consequential election season, law enforcement and intelligence groups have been warning that violence or unrest poses a threat to Tuesday’s election—and what could come next.

We’re already seeing it: Ballot boxes in the Pacific Northwest have been set ablaze with incendiary devices. A Texas man allegedly punched a 69-year-old poll worker after he was asked to remove his MAGA hat. And a recent report from the University of Pennsylvania found that “civil unrest in the face of the 2024 presidential election and beyond is a realistic if not likely possibility.”

That report touches on a once-unfathomable question that’s been getting a lot of attention recently: Could the military be called on to quell election-related violence in America’s streets?

Governors in three states have already announced they are putting National Guard units on standby. So the short answer is yes. The slightly longer answer is yes—with a lot of “it depends.” The even longer answer is that some of those “it depends” deeply worry legal experts.

“I think that we are at a point when the rule of law is in a profoundly fragile position in this country,” said Claire Finkelstein, director of the Center for Ethics and the Rule of Law at UPenn, which ran the exercise.

Read on.

Q. Who can deploy the military?

A. The first thing to know is that the military cannot just “step in” on Election Day—as some people are falsely claiming on social media—or any other day. Any decision to deploy troops domestically needs to come from a legal or constitutional authority.

That’s typically the president or, in the case of the National Guard, a state governor. In some cases, the Defense Department may authorize troops in response to a request for specific assistance from civilian law enforcement. But those requests are closely examined by the military and if they’re approved, troops would only be deployed in a support role to a specific civilian agency. The Pentagon cannot sign off on a general request for support on election day “if” things get rowdy, or if the election doesn’t go a certain way.

Q. What’s the difference between the National Guard and active-duty troops deploying on U.S. soil?

A. The National Guard is a unique force. Most of the time, it’s under the command of a state governor, who can use Guardsmen for any number of missions in their state—responding to natural disasters, filling in as healthcare workers during a pandemic, patrolling the subway over crime concerns. State governors can also lend their National Guard units to other states that request them. For instance, 14 states have sent Guard units to the southern border at Texas Gov. Greg Abbott’s request.

But the president can also federalize National Guard troops, or bring them under presidential control. In that case, they’re considered the same as active duty military troops and are subject to certain additional safeguards to ensure we don’t use the military as a domestic police force.

Q. What are those safeguards?

A. The big one is called the Posse Comitatus Act, a law dating back to the Reconstruction era after the Civil War. It prevents the military from acting in a law enforcement capacity. That means that under normal circumstances, the military—including National Guard troops under presidential control—can’t start searching or arresting protestors if there were demonstrations after the election or on Inauguration Day.

Q. Are there other limits on what the military could do specifically on election day?

A. There absolutely are. U.S. law expressly forbids “troops or armed men” at polling places. It also forbids members of the military from preventing or trying to prevent citizens from voting. The Defense Department doubles down on this in its internal policy, stating clearly that soldiers and federalized Guardsmen “will not conduct operations at polling places.”

It makes sense that federal troops should not be mixed up in the electoral process, says Lindsay Cohn, a national security professor at the Naval War College.

“The federal government is not in charge of elections,” she said. “Elections are run by the states.”

Q. Are there any exceptions to the rule?

A. There’s one. The law allows for the presence of military troops at a voting site to “repel armed enemies of the United States.”

It’s not entirely clear what might constitute an “enemy” at a polling place, Finkelstein said. “Presidents have traditionally had the authority to decide who is an enemy of the United States.”

It’s likely it could apply to domestic, not just foreign, actors. But if the military were to deploy for some reason at a polling site under this exception, the question would ultimately probably end up in the courts.

It’s also important to note that the prohibition only applies to federal troops—not the National Guard, if it’s under the command of a state governor.

Q. So, National Guard units under state control could be called up on election day?

A. That’s right. Nevada Gov. Joe Lombardo announced last week that 60 Nevada National Guardsmen will be standing by on election day to support law enforcement if needed, though he said in a statement that he did not expect them to actually be deployed. The governors of Washington and Oregon have also ordered Guard troops to stand by during election week.

Some states do have laws that forbid military or law enforcement officers from being present at election sites. For instance, Pennsylvania law prohibits “troops in the Army of the United States or of this Commonwealth” from coming within 100 feet of a polling site unless they’re voting. But not every state forbids it, and the National Guard is often used to provide election security, both physically and digitally.

During the Covid-19 pandemic, National Guardsmen even filled in as poll workers. Guard units also deployed to provide security at state capitol buildings after Jan. 6.

Q. Is there anything the National Guard can’t do around the election?

A. Governors have a lot of leeway in mobilizing their National Guards. But the decision to activate Guard units domestically typically comes only after in-depth planning discussions between National Guard and state leadership, says Gen. Daryl Bohac, who served as Nebraska’s adjutant general for 10 years.

“Public trust is so important to the military and its ability to operate no matter where we are, whether it’s in the states or abroad,” Bohac says.

Still, retired officers have been sounding the alarm about the potential for National Guard deployments to become politicized. This summer, Bohac, along with other former military officials at Count Every Hero, a group of retired generals and admirals working in defense of democracy, released a set of principles to help guide the decision to deploy the National Guard domestically, emphasizing the need for a deliberative, apolitical planning process and the importance of exercising extreme caution around elections.

Ultimately, the choice largely lies with a state’s governor. And National Guard troops deployed under the command of their governor are not subject to the federal Posse Comitatus Act, meaning they can directly assist civilian law enforcement with police activities.

Q. Are there any other exceptions to the Posse Comitatus Act?

A. Yes, but most of them don’t come into play around the election or the transfer of presidential power—except for one: the Insurrection Act.

Q. Wait—what’s the Insurrection Act?

A. The Insurrection Act is a set of laws dating back to the earliest days of our country that give the president broad authority to mobilize the military to suppress a rebellion or other unrest that “make it impracticable to enforce the laws of the United States.”

Q. Can troops do anything under the Insurrection Act?

A. No. Invoking the Insurrection Act does not suspend the Constitution or other civil liberty protections. Military troops deployed under the Insurrection Act still have to respect things like the 4th and 5th Amendments—no unreasonable searches and seizures, no taking life, liberty, or property without due process of law—just as law enforcement officers do.

But the Insurrection Act effectively leaves it up to the president to unilaterally determine what might constitute a rebellion, and to decide when to invoke his or her authority to call up the military to address it.

“Historically, the constraints on that have been political norms, historical norms, just general concerns about civil-military relations and the military’s reluctance to get involved in civilian affairs,” says Mark Nevitt, a former Navy JAG officer and a professor at Emory Law School.

“But that’s a norm, not the law.”

Q. When is the last time a president invoked the Insurrection Act?

A. We’re actually in the longest period in which the Insurrection Act hasn’t been invoked. In the past, both Democratic and Republican presidents have used the act to enforce calm or to protect civil rights, as when President Eisenhower federalized the Arkansas National Guard to ensure school desegregation in the South. The last time a president invoked the Insurrection Act was during the 1992 riots after the police beating of Rodney King.

When former President Trump has talked about deploying the military against civilian protestors, legal experts believe the justification would likely come from the Insurrection Act. During the Black Lives Matter protests in the summer of 2020, the Trump administration reportedly drafted, but did not implement, an order invoking the Insurrection Act.

At the time, then-Secretary of Defense Mark Esper told reporters he did not support invoking the act.