Recent comments by President-elect Donald Trump about his plans to use the U.S. military on domestic soil have sparked controversy and confusion. On the campaign trail, Trump warned about the “enemy from within,” suggesting he would use the National Guard and U.S. active-duty military personnel to silence political opposition. More recently, Trump indicated he would use “military assets” to assist in mass deportations.
When can a U.S. president deploy the military inside the United States? Trump’s first presidency was marked by widespread confusion on this question – about what was legal and what was appropriate. The analysis here attempts to clear up some of this confusion regarding the limits and norms surrounding presidential authority when it comes to the use of the military.
What authority does the president hold over the military?
The U.S. Constitution names the president as the commander-in-chief of the armed forces, at the top of the chain of military command. While Congress has the constitutional authority to declare war and to fund (or not fund) military actions, presidents have expanded the scope of their war powers over time through their own actions. At times, Congress has also explicitly or implicitly delegated this power to the president.
The president, thus, has significant discretion over how the military is used, both internationally and domestically. This has led to criticism of Congress’ ability and willingness to rein in the executive branch when it comes to the use of force.
Many of the activities Trump has proposed may violate longstanding norms, as well as U.S. public preferences about the appropriate use of the armed forces. But it isn’t clear that such actions would be unlawful under the president’s powers.
Specifically, under 10 USC 13 sections 251 through 255, Congress has delegated to the president the power to:
- Respond with federal active duty forces or federalized National Guard forces to a state’s request for aid against an insurrection within the state (sec 251).
- Use federal active duty forces or federalized National Guard forces to enforce federal law and suppress rebellion “whenever the president considers that unlawful obstructions, combinations, or assemblages, or rebellion against the authority of the United States, make it impracticable to enforce the laws of the United States in any state by the ordinary course of judicial proceedings” (sec 252).
- Use the National Guard, the active duty forces, “or any other means” to “take such measures as he considers necessary to suppress, in any state, any insurrection, domestic violence, unlawful combination, or conspiracy” if he thinks that situation deprives any part of the people of that state of a federally-guaranteed right, privilege, or immunity, and the state is unable or unwilling to protect those rights (sec 253).
These provisions give the president discretion to determine when a situation warrants intervention, and the Supreme Court has opined that such a determination by the president is not subject to judicial review (Martin v. Mott 25 U.S. 19, 1827). The president can call the state National Guard into federal service without any participation from Congress. If the president wants to avoid invoking the Insurrection Act, he can also use 32 USC 502(f), which allows a governor to order their National Guard to support a presidentially ordered mission paid for by the federal government, but remain in state status. This provision is less flexible, as National Guard troops in this status technically cannot be sent into another state that does not accept their presence – but they could be used within willing states to enforce federal immigration law, for instance.
In short, the president has the authority to determine when a situation requires federal armed intervention. And the president has the statutory authority to order that intervention with neither prior authorization from Congress, nor judicial review.
The president now has broad immunity
Moreover, the Supreme Court’s recent immunity decision in Trump v. United States grants the president total immunity from criminal liability for official acts taken using core powers. The ruling also confers presumptive immunity for other official acts.
Of course, immunity does not in itself make any and all presidential actions legal; rather, it insulates the president from legal consequences. The president could be impeached for unlawful behavior, but impeachment and removal from office is a political process that would almost certainly require bipartisan support in the House to impeach, and then in the Senate to convict.
What might constitute an unlawful order?
Those in the military carrying out the president’s orders, however, are not protected by presidential immunity. This means military personnel could be prosecuted for following an “unlawful order.” According to the Uniform Code of Military Justice (UCMJ), lawful orders are those that are reasonably specific, do not conflict with constitutional or statutory rights, and have a military purpose. Even when orders fail to objectively meet this criteria, it could be difficult to prove. And it isn’t always clear to the service member on the ground, or even their chain of command, what constitutes a lawful versus unlawful order.
Military officers serving in the executive branch do not have the final word on the legality of legal orders. Rather, civilian appointees at the Department of Justice can make such determinations, which are then binding on military commanders until (and unless) federal courts overrule it. One example of this process was the debate over the legality of torture during the George W. Bush presidency.
The courts have a history of granting deference to the government on issues of national security and military policy. In Korematsu v. United States, for instance, the Supreme Court ruled that it was legal to intern American citizens based on their Japanese ancestry, given a national security justification.
Contrary to conventional wisdom, “I was following orders” is a valid legal defense for members of the military unless the order is “manifestly unlawful,” an intentionally high bar given the chaos that would result if every soldier acted as a Supreme Court of one. Conversely, moral or ethical concerns are not legal grounds for disobeying a lawful order under the UCMJ – and a soldier who did so might still find themself facing punishment.
The president does have broad pardon power, which could be used to protect those following unlawful orders from legal consequences. Trump, in particular, has proven willing to intercede in the military justice system. In 2019, for example, Trump intervened in the cases of three military service members accused of war crimes.
But doesn’t Posse Comitatus prevent the military from being used domestically?
In short, no. The 1878 post-Reconstruction era Posse Comitatus Act (as amended) states that whoever uses any of the federal armed forces “as a posse comitatus or otherwise to execute the laws” – “except in cases and under circumstances expressly authorized by the Constitution or Act of Congress” – is liable to moderate fine or imprisonment. But this law notably does not restrict the use of the military domestically for issues that would fall under the Insurrection Act of 1807 (described above). [That act delegated to the president the use of the federal armed forces or the calling out of state forces for repelling invasion, suppressing insurrection, or executing the laws of the union.] The Posse Comitatus Act also does not restrict the activities of National Guard units when they are operating under state control.
While this does not mean the president has carte blanche to use military forces domestically, the president has broad discretion to determine when circumstances require the White House to intervene with the armed forces. So in this case, the constraints on the president are political – as they so often are in matters of national security.
Of course, the political nature of using the military on domestic soil cuts both ways. A lack of legal constraint does not mean that the president-elect won’t incur political pushback from Congress and/or the public for his actions, especially if he follows through on the threat to use the military to pursue political opponents he deemed an “enemy from within.”
Who actually controls the National Guard?
The National Guard holds a unique place in the armed forces. By default, each state’s National Guard unit is under the operational authority of the governor and the laws of that state. An exception is the DC National Guard, which always reports to the president (through the secretary of defense) as the city of Washington, DC, has no governor. Since the National Guard is also a federal reserve component, the Department of Defense has authority over most training, equipment, and personnel requirements. And the Pentagon can order National Guard forces into federal service, such as during the war in Iraq.
This dual status of the National Guard can create tension, particularly when the political agendas of governors and the president conflict. Texas Governor Greg Abbott (R), for example, has challenged the Department of Defense’s authority, repeatedly deploying the Texas National Guard to the southern border. Surveys of the soldiers involved revealed many were angry and frustrated by the involuntary deployment.
Even in the absence of such direct tension, discussion of National Guard forces as belonging to “red” or “blue” states risks associating the use of the military for explicitly partisan ends. For example, 25 of 27 GOP governors signed a letter supporting Abbott’s mobilization of National Guard resources – in what amounted to a political standoff between state and federal authorities over immigration law enforcement. Over a dozen of these governors sent National Guard forces under state deployments to the border in support of the mission. In June 2020, nearly all of the 3,800 troops that answered the Trump administration’s call for National Guard forces to control crowds in Washington, DC, following the death of George Floyd came from states led by Republican governors.
What does all this mean for civil-military relations?
The broader concern about the incoming administration is that Trump’s proposed uses of the military can deepen the partisan divide in America and draw the armed forces further into partisan disputes. The domestic military deployments the incoming Trump administration appears to be contemplating would go against long-standing American traditions – and head well beyond what many in the U.S. public and the military consider appropriate use of military personnel. Military deployments on U.S. soil may risk the public’s high level of confidence in the military, and even harm military recruiting and retention if current and prospective service members do not wish to be involved in domestic actions.
Danielle Lupton is a political scientist who studies civil-military relations, public opinion, and foreign policy. She is an associate professor of political science at Colgate University.
Jessica Blankshain is a political scientist who studies civil-military relations and foreign policy decision-making. She is an associate professor of national security affairs at the U.S. Naval War College.
David Burbach is a political scientist who studies civil-military relations and space security. He is an associate professor of national security affairs at the U.S. Naval War College.
Lindsay Cohn is a political scientist who studies civil-military relations, public opinion, and militarized policing. She is an associate professor at the U.S. Naval War College and a visiting associate professor at Columbia’s SIPA.
Theo Milonopoulos is a political scientist who studies civil-military relations, decision-making, and emerging technologies. He is an assistant professor of national security affairs at the U.S. Naval War College.
All views and insights expressed here are the authors’ own and do not necessarily represent the views of the U.S. Naval War College or the U.S. government.
