The Just Security Podcast

What Just Happened Series: Potential U.S. Military Domestic Deployment for Immigration Enforcement

• Just Security • Episode 97

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In his second term in office, President Donald Trump has already taken sweeping measures on immigration, the environment, the U.S. military, and the structure of the federal government.

With so many executive orders, policy changes, and novel actions, it’s easy to wonder, “What just happened?” In this podcast mini-series we help to answer exactly that question.

On each episode of “What Just Happened,” we’ll talk with leading experts, from former government officials to professors – the people who understand how government works from the inside and have studied the issues for years. They will explain the legal background and implications of how the Trump administration’s actions affect how the U.S. government operates in Washington, across the country, and around the world. 

This is not a political podcast. We are explaining the meaning and consequences of policy changes that may not be immediately apparent. Any opinions expressed are those of the speaker.

Today, we will focus on President Trump’s potential deployment of the U.S. military. Trump has said that he intends to use more military resources to support border and immigration enforcement. Joining the show is Mark Nevitt. Mark is a professor at Emory University School of Law. Mark was previously a Commander in the Navy, where he was a tactical aviator and a JAG officer.

This mini-series is co-hosted by David Aaron, Tess Bridgeman, and Ryan Goodman. 

Show Notes: 

Ryan Goodman: In his second term in office, President Donald Trump has already taken sweeping measures on immigration, the environment, the U.S. military, and the structure of the federal government. 

With so many executive orders, policy changes, and novel actions, it’s easy to wonder, “What just happened?” In this podcast mini-series, we help to answer exactly that question. I’m Just Security’s Co-Editor-in-Chief, Ryan Goodman. 

David Aaron: And I’m David Aaron, a former federal prosecutor with the Department of Justice’s National Security Division and a visiting professor at Wesleyan University. On each episode of “What Just Happened,” we’ll talk with leading experts, from former government officials to professors — the people who understand how government works from the inside and have studied the issues for years. They will explain the legal background and implications of how the Trump administration’s actions affect how the U.S. government operates in Washington, across the country, and around the world. 

This is not a political podcast. We are explaining the meaning and consequences of policy changes that may not be immediately apparent. Any opinions expressed are those of the speaker.

Today, we will focus on President Trump’s potential deployment of the U.S. military. President Trump has stated that he intends to use more military resources to support border and immigration enforcement. Joining the show is Mark Nevitt. Mark is a professor at Emory University School of Law. Mark was previously a Commander in the U.S. Navy, where he was a tactical aviator and a JAG officer. 

Mark, welcome to the show. President Trump has said he would like to deploy the U.S. military domestically to support his immigration and border enforcement agenda. So far, this seems to involve declaring a national emergency at the southern border, using the Department of Defense to seal the borders and maintain U.S. territorial integrity, sovereignty and security, supporting DHS activities to control the southern border, and assisting law enforcement with border security. A lot of the specific wording has important legal significance. So, before we look at what these directives mean and separate out legal constraints from policy decisions, what are the fundamental laws and regulations that either enable or limit the use of the military domestically?

Mark Nevitt: Great, David, and thanks for having me on the program. So, I think of this question as exactly as you laid it out. There's sort of enabling laws and there's limitation laws, or limiting laws. And so, the enabling laws, I think of really three enabling laws, which include, of course, the Insurrection Act, which the president can invoke to federalize either the National Guard or the federal military forces, what your listeners may think of as Title 10 military forces. Second, there's the National Emergencies Act, which has been declared at the border by President Trump. That really just kind of facilitates activation of reservists on there's some kind of obscure authorities that are in Title 10. And the third, sort of, enabling authority is called 502(f), which has not been invoked yet, but is an authority that was used in 2020 when President Trump and Attorney General Barr essentially requested the National Guard from other states to provide — I'm using air quotes — “other duty” in support of the DC, sort of, protests in the summer of 2020.

So, those are sort of the three enabling statutes — Insurrection Act, National Emergencies Act, and this sort of under theorized 502 authority. There's also limitations. And the limitations are — probably the most prominent one your listeners are familiar with are the Posse Comitatus Act, and I'm happy to talk about that in just a second, which basically limits the active-duty federal military forces from being used in the law enforcement capacity. There's also case law, which sort of describes the Posse Comitatus Act. And that's sort of the second limiting factor. Courts have been somewhat engaged on limiting the military's role in domestic operations in the 1970s and 80s, most predominantly. And then just the third, which is, I think, is really important and is maybe underappreciated, is, I think, military regulations — how the military interprets its own authority — as well as military doctrine — how the military basically issues orders, how the military guides its operations, and that's in a variety of joint publications which govern military operations domestically

David: So, that's a lot, thank you. All from memory. You mentioned the Posse Comitatus Act, and that's getting a lot of discussion right now in the media and elsewhere. Can you just briefly describe what does the Posse Comitatus Act allow and not allow? 

Mark: Sure, and the Posse Comitatus Act is a statute. It's actually not from the nation's founding, which some people think it is. It's not. It actually came about in 1878 and corresponded with the end of Reconstruction, when many Union troops were basically enforcing civil rights laws in the South. And that was actually a time when the military was actually used as a sort of protection, sort of, protector of civil liberties in the American South. 

And so, it's actually worth it maybe for me to kind of paraphrase what the actual statute says.  And I talked about in the article, but it says essentially that, except in cases and other circumstances authorized by the Constitution or acts of Congress, anyone that uses any part of the Army, Navy, Marine Corps, Air Force or the Space Force as a posse comitatus to execute the laws shall be fined under this title or imprisoned not more than two years. And so, it's a criminal law. It's a criminal statute, and it basically prohibits anyone, a military commander or someone in sort of a chain of command. from using the military in a law enforcement capacity. We're sort of stuck with this term posse comitatus, which comes about from, you know, the American West, when actually some of the fewest people out in the American West were army outposts, and they were used in the law enforcement capacity. So, we're kind of stuck with this term. But, you know, the blanket prohibition is I think used as a law enforcement role for these military service members. Of course, there's two exceptions, and one says the act of Congress or something that's authorized by the Constitution. So, those are sort of the exceptions, David, to the posse comitatus, and the most prominent exception is probably the Insurrection Act, which is understood to be an explicit exception to the Posse Comitatus Act.

Ryan: So, just wanted to actually touch down on that particular point. Is one of the executive orders, the one that's titled, “Clarifying the Military’s Role in Protecting the Territorial Integrity of the United States,” is it another kind of an end run around the Posse Comitatus Act? So, just exactly the way you described it, Mark, that the Posse Comitatus Act prohibits the use of military force for law enforcement. But lo and behold, one way of understanding that executive order is it says, okay, the military will be used to police the border, but as a pure-blooded military operation — not law enforcement at all. And it's kind of not where people had been looking for how the administration might try to deal with the Posse Comitatus Act, and if indeed it's a full-blown military operation, the greater power includes the lesser of arrests and detention of individuals as part of that military campaign. Is that a way to think about what might be going on inside that executive order?  

Mark: Yeah, you keyed on, Ryan, the same thing that I keyed on when I read the two executive orders, because there is, in fact, an executive order declaring a border emergency, a border security emergency, which has some discussion of the military's role, but the second executive order is exactly that — clarifying the military's role and protecting the integrity, territorial integrity, of the United States. And I read this second executive order as being potentially a way to maximize the military's role at the border. 

And that's really essentially governed by what's called the military purpose doctrine, which is sort of an underappreciated doctrine that kind of raised its head around 2001 in the aftermath of September 11, when John Yoo issued an OLC memorandum, essentially giving more authority to the military domestically in the fight against terrorism. So, there's always been a little bit of sort of uncertainty between what exactly is a law enforcement function, what exactly is a sort of fighting terrorism, traditional military function. And so, I read this as potentially a way for the Secretary of Defense, Secretary Hegseth, and President Trump to use the military more towards a military purpose, more towards maybe the John Yoo version of how the military would be operating at the border.

And this is a legal gray area. After 2001, that OLC memo was clarified in 2008 which more circumscribed the military's role in domestic operations, but you know, we'll see who’s at Department of Justice. There's a lot of shake up happening right now. Who's going to be the OLC, who's going to be writing the opinions, who's going to be interpreting the military purpose at the border. And that's why I think that second executive order may be trying to sort of drive a truck through the military purpose doctrine. 

Ryan: And just a quick follow up. Do you think it might therefore also dovetail with the executive order on declaring certain cartels foreign terrorist organizations? Because if they are indeed terrorist organizations, then seems like we're closer to the John Yoo rationale of counterterrorism domestically might very well allow for the use of the military in a certain under certain conditions.

Mark: I think that's right. I think Trump's reference to, I'm using air quotes, “immigrant invasion,” and his designation of certain cartels as a foreign terrorist organization, that just sort of further blurs the line, I think, between law enforcement and traditional military activities that sort of really define the military purpose doctrine. You know, big picture, I think, of, what is law enforcement? Law enforcement is searching, arresting, stopping, seizing, you know, basically doing police type actions domestically. What is sort of a military’s purpose? That's fighting and winning the nation's wars, right? If there's sort of an invasion in the content of what President Trump is calling, then again, I think — and he’s declaring certain cartels, foreign terrorist organizations, and he's using that word terrorist, which is exactly what the 2001 OLC opinion keyed on was the role of the military fighting terrorism — again, I think it's a further blurring of the line, Ryan, between these law enforcement and traditional military activities.

Ryan: Can we just pivot back to the Insurrection Act? Because that might be an important mechanism that the administration uses either in the context of immigration or maybe down the line in the context of political, civil unrest. So, one commonly described interpretation of the Insurrection Act is that it’s very open ended. That there aren't too many constraints on the president's ability to declare an emergency under the Insurrection Act of a sort, or just to invoke the Insurrection Act, let's say. But is that right? So, I guess the question to you is, and I can't think of in a sense of a better person as the question, do the terms of the Insurrection Act really read that broadly, or are they, in fact, narrower, and narrower in the sense that the kind of unrest or rampant criminality must rise to a different kind of a threshold, and that threshold is one in which the criminality or the like is a flat rejection of governmental power, of court orders, or is in fact an attempt to overturn governmental authority. Is that a better way of reading it? Or how do you think is the best way of reading it? How do you think courts would read it if they got the opportunity to actually ever reach the merits on something like that? 

Mark: Yeah, this is sort of the big question in the room, and this is how my article ends, is discussion of this Insurrection Act. So, this could be if an Insurrection Act is invoked. And it's important to note to your listeners that the insurrection Act has not yet been invoked. There's a lot of thought that President Trump might actually invoke the Insurrection Act on day one. He did not do that. And I should also note that this is the longest time in American history where we've seen an Insurrection Act invocation. The last time we've seen an Insurrection Act invocation was in 1992 during the Los Angeles riots.  

So fundamentally, Ryan, I think most commentators agree, regardless of the political aisle they're on, that an Insurrection Act invocation does not actually require an insurrection. You can look at the terms of the statute, which have not been really updated since 18, I guess, 70s, is when the last time the Insurrection Act was updated. And so, one could interpret an Insurrection Act to enforce federal law or suppress a rebellion against U.S. authority. And so, by the terms and plain language of the insurrection, one read of it is that it is, in fact, you know, fairly wide open, particularly one provision which is 10 U.S.C. § 2253, which is the more open-ended provision, which, by the way, does not require the governor of a respective state to request presidential assistance. 

So, long way of saying, I think it is open ended, number one, Ryan, more open ended than I am comfortable with, which I've written in Just Security previously that we need to have Insurrection Act reform. It strikes me as completely reasonable that if we are going to have some kind of military deployment overseas, we should have a congressional role in sort of a war powers-like resolution or some kind of check on the president if he was to deploy the military domestically, and it just seems to be common sense. There was some good reading and research, and I'd point you to the work of Laura Dickinson on looking at the OLC opinion. She does a really nice job in a forthcoming article in the Harvard National Security Journal, basically walking through the history of these OLC opinions. And she makes a really compelling argument that we should be viewing the Insurrection Act more narrowly than maybe making it out to be. The reason why I'm a little bit cautious of co-signing to her view is that I just think we don't know the OLC’s current view of the Insurrection Act and who will be in there at Department of Justice, and I think it'll be more towards a maximalist approach of this.

So, long way of saying, Insurrection Act hasn't been evoked, certainly does not involve an insurrection, and is an open question of whether or not an invocation of the Insurrection Act is even open for judicial review. There's some case law to suggest maybe that it is, and somewhat mixed case law to suggest that it's not. So, we shall see.

David: Thanks, Mark. So, we've talked about some limits on presidential authority to use the military in some of these capacities, but the president is the commander-in-chief. As the commander-in-chief, what authority does he have to decide how and when to deploy military personnel, military assets domestically, including for purposes like logistical support, reconnaissance, surveillance, intelligence, that kind of thing. What can the president do within the bounds, clear bounds of the law? 

Mark: With the clear bounds of law, he certainly can order active-duty military troops to the border within his authority as commander-in-chief. And I should note that every president, I think since President Clinton, has had some kind of military presence at the border. So, we have, I think, 1,500 Army and Marines that were just ordered two days ago, what's called an operational order to go to the military border, and they're joining 2,500 troops that are already there under President Biden. So, the president clearly has the authority to do that under his role as commander-in-chief. 

And the president, as part of his authorities, the military could do any sort of indirect support, right? That's surveillance, detection, monitoring. You're seeing military flights to Colombia and elsewhere, Guatemala — logistical, administrative support. That is something that is clearly within how the DoD the military interprets its instructions and interprets its authority. So, the president can certainly do that under commander-in-chief authority. There's another question that the executive orders get to about this notion of invasion, and I think that this sort of a murky area of authority that is worth, you know, tying out that I speak to about securing our borders against threats of invasion. The president seems to be suggesting that under the guarantee clause, which says that the United States “shall guarantee to every State in the Union a Republican Form of Government and shall protect each of them against Invasion,” he's tying the invasion language of the Constitution with the invasion language of what's happening at the border pursuant to his executive order. So, the president may be thinking that there's sort of a take here, Article II authority, that he's trying to guarantee to the state of Texas, Arizona, California, of protecting those states from — and I'm using air quotes — “invasion.” And so, that's how I read, potentially, that authority. But that's not clear by any means, David, about the president's ability to do that.

David: Thank you. And then turning to Congress, to what degree does Congress have an oversight role in the president's deployments?  

Mark: So, I view the Congress as really critical, and the president, broadly speaking, the commander-in-chief, has the power of the sword and the Congress has the power of the purse, and so at some point, the president has to get fiscal authority, right? He's got some sort of recurring authority that is in place where Congress has essentially given the president sort of a $6 billion runway to basically reprogram money from one mission to another mission. That is, sounds like a lot, but the U.S. military's budget is around $800-900 billion a year, and so it's less than one percent of the military's budget. So, Congress, at some point, I think, has to act, David, or the troops have to go home. And I will say this. The National Defense Authorization Act, the defense spending bill, that's really the one act of Congress that Congress has to pass every year, right, to fund the military. And that's really, really specific in terms of what exactly is in those provisions. And so, that's going to be a very interesting discussion this springtime, into the summer, when that bill goes before the Armed Services Committee about what Congress's role is in these military deployments. But the president certainly has a runway. How long that is? I don't know exactly, but it's certainly not indefinite. I think it's a 2025 runway. Beyond that, I would think Congress has to act.

David: And if the end of the runway is reached and Congress has not acted, and the president does not withdraw the troops, is there any precedent for that? Or do we know what would happen. 

Mark: Right. Well, so, then it would be a violation of appropriations law, a violation of fiscal law, a violation of statutes like the Antideficiency Act. So, I think you'd have a lot of pushback from the Pentagon about, show me the authority to, you know, continue this military operation under what fiscal authority. And so, I think that's real. I think that the bean counters at the Pentagon and beyond will be looking at this very, very closely. And I don't think people are going to be too excited to be openly violating the law if there's no fiscal authority to do so.

David: Excellent. Thank you. So, short of that, looking forward, is there any type of particular conduct you think people should be watching for to assess whether the military has taken on a very different role than it's previously taken on when it comes to the border or immigration, anything that requires or operates under a different set of legal authorities, anything people in the audience should be keeping an eye out for?

Mark: Yeah, let's keep an eye on what their military is doing at the border, right? Unfortunately, the executive orders have tasked U.S. Northern Command, which is the combatting command in charge of, really, this main mission to basically come up with a plan in the next 30-some-odd days. That plan is going to be classified. And so, what we'll know is really what's on the ground, in terms of who is, you know, what the military is actually doing on the ground. And so, I would think, I would hope, David, that this would be consistent with prior military deployments under Biden, Obama, Trump, fill in the blank, at the border. But if we're seeing more of a role in immigration enforcement and more of a role in this search, arrest, seizure, then I start to think, I'm starting to get more and more concerned. 

And so that's what I'm sort of looking for, sort of the facts on the border. I should note that I was somewhat surprised, and I think this time you have to be a little bit, find the silver lining. And so, here's a silver lining for me. At least there was no discussion of the military doing interior border security — going to Chicago, going to — I'm in Atlanta. There was just a raid here in a church over the weekend with ICE agents. The military was — is — not tasked to do sort of interior law enforcement, or even interior, sort of, support to law enforcement within the confines of sort of the interior part of the United States. So, that's sort of what I'm looking for. But again, in 90 days, the Secretary of Defense has been asked to give some sort of recommendation to the president on Insurrection Act authorities, so we'll know about that in a few months.

David: Mark, Thanks again so much for helping us understand what just happened and giving us context to watch for what comes next. Mark's recent article for Just Security’s What Just Happened series, “Unpacking Exec Order on National Emergency at the Southern Border” is a must read on the topics we just discussed.

Ryan: “What Just Happened” is a mini-series of the Just Security Podcast.  This episode was co-hosted by me, Ryan Goodman and David Aaron. It was produced and edited by Paras Shah with help from Clara Apt. 

Special thanks to Mark Nevitt. You can read all of Just Security’s coverage of the Trump administration, including Mark’s analysis, on our website. If you enjoyed this episode, please give us a five-star rating on Apple Podcasts or wherever you listen.

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