Will Trump Send the Military to Seize Illegal Immigrants?

Photo by Clay Banks on Unsplash

The dominant theme of this Substack is to call out Donald Trump’s abuses of executive power that violate constitutional rules and bedrock social norms. During the campaign, these overreaches were more obvious—Trump would shout generalities from the rooftops, such as promising reprisal prosecutions against his antagonists in the DOJ and in the states. Now, his actions are more subtle: you need to understand the constitutional backdrop and norms to identify them. That’s what I aim to do here.

Last time, we discussed how Trump’s proposal for recess appointments undermines the Senate’s constitutional role of advice and consent. This dispatch focuses on the similar effects of his announcement that he plans to use the armed forces to execute the largest deportation of immigrants in U.S. history.

Harry Litman's First Substack Post - Constitution in Crisis - Bulletin 1

On Monday, Trump responded to a social media post from the president of Judicial Watch, who claimed Trump would “use military assets” for a mass deportation program. Trump tweeted back, “TRUE!!!” (naturally, in all caps and with three exclamation points). Trump’s closest immigration adviser, recently appointed Deputy Chief of Staff Stephen Miller, has also promised a “100 percent perfect deportation rate.”

We don’t know the full details of the plan—nor, perhaps, does Trump himself. But what we do know is deeply troubling.

As a society, we share an unease with the idea of the armed forces being used for tasks meant for domestic law enforcement. Deploying the military for such purposes is a deep taboo in American society for good reason.

Maintaining a clear line between civilian and military functions is fundamental to the national commitment to civil liberties. Immigration enforcement in the United States falls under civilian agencies such as U.S. Customs and Border Protection (CBP) or Immigration and Customs Enforcement (ICE). The military plays no role in this process.

This principle—that military forces should steer clear of domestic law enforcement—is a bedrock idea not only in the United States but in nearly all democratic nations. It stems from historical experiences with authoritarian regimes, where military forces are often used to suppress dissent. In democracies, the distinction is clear: the armed forces defend the nation from foreign threats, while civilian law enforcement addresses antisocial behavior within society, ensuring due process and protecting individual rights.

In the United States, this line can be traced back to the Reconstruction era, a period that, in many ways, mirrors the Trump era. After the Civil War, federal troops occupied the South, provoking widespread resentment. In response, the Posse Comitatus Act of 1878 was enacted. The law prohibits the use of the Army—and later the Air Force—for domestic law enforcement, except where explicitly authorized by Congress or the Constitution. (The Department of Defense later expanded this prohibition to include the Navy and Marine Corps.)

Exceptions to Posse Comitatus are rare and primarily governed by the Insurrection Act of 1807, which permits military involvement in domestic law enforcement in cases of insurrection, rebellion, or when civilian authorities are unable to enforce federal law. This has happened only a handful of times in U.S. history.

One example was the 1992 Los Angeles riots following the not-guilty verdict in the first Rodney King trial. At the time, I was at the Department of Justice and involved in the legal intricacies of declaring an emergency. Local law enforcement was completely overrun, and the military’s intervention was necessary to restore order.

Another well-known example occurred during the Eisenhower administration when federal troops were deployed to enforce the integration of Little Rock schools. Here, local law enforcement had willfully refused to uphold constitutional rights, requiring military action to enforce the law.

Even in extraordinary situations, the military’s role is limited. It can provide logistical support to civilian agencies but cannot enforce immigration laws or apprehend migrants. Trump controversially used this support function in 2018 when military personnel assisted CBP with surveillance at the border.

Now, Trump appears to want to go much further, proposing the direct involvement of military personnel in rounding up undocumented immigrants for deportation.

Trump justifies this unprecedented use of the military by declaring an “emergency” driven by extreme illegal immigration—a narrative he’s crafted about hordes of violent immigrants pouring over the southern border. Even if the situation were as dire as he claims, deploying the military in this way would violate the Posse Comitatus Act and the principles it embodies.

Such a move would amount to a dystopian nightmare. Imagine armed troops with rifles entering communities to detain undocumented immigrants for immediate deportation. This vision would horrify the nation and likely bring widespread shame.

Trump seems to believe that simply declaring an “emergency” gives him unlimited power to bypass constitutional traditions. However, the southern border has been a semi-permeable boundary for decades. While immigration enforcement is a challenge requiring legislative solutions, it is no justification for military intervention.

Presidential declarations of emergencies have become increasingly common. More than 60 national emergencies have been declared, over half of which remain in effect. These declarations are typically used to unlock federal resources—not to authorize the military to enforce domestic law. Even in Trump’s 2019 border “emergency,” military involvement was limited to logistical support, not direct enforcement.

Although Congress technically has the power to terminate a national emergency, it’s a near impossibility in today’s political climate. Terminating an emergency would require a joint resolution and a two-thirds majority in both houses to override a presidential veto—an unrealistic scenario.

Trump may also consider calling on state militias or activating the National Guard. While this might technically fall within his emergency powers, it would still contravene the strong social consensus against using military authority for domestic law enforcement. The image of state militias or National Guard members pulling migrants from their homes is hardly less unsettling than federal troops doing the same.

If Trump proceeds, he may invoke the idea of an emergency to justify novel uses of military power. While political theorists like Locke and Montesquieu acknowledged that the executive might sometimes depart from legal norms in extreme situations, U.S. constitutional law—as reinforced in cases like the Steel Seizure Case—requires congressional authorization for such actions.

The deeper issue is Trump’s ongoing effort to stretch, if not tear, the constitutional fabric by undermining the principle that we do not use the armed forces for domestic law enforcement. Whether through the National Guard, state militias, or some expanded “emergency” power, Trump’s proposals threaten to degrade our national identity and edge the U.S. closer to autocratic regimes like Hungary or Argentina during its Dirty War.

With a Republican-dominated Congress largely organized around loyalty to Trump and a Supreme Court willing to endorse expansive executive powers, who is left to stop him?