Our recent lunch event, co-hosted by the National Security and Military Law Society and the Federalist Society, with Professor Nevitt and Professor Markovitch offered a timely “101” on the legal architecture, and the real-world risks, surrounding domestic deployment of U.S. military forces. The discussion focused on how American law tries to preserve a core constitutional tradition: the military is not a domestic police force, and when it is used at home, it should be under narrow, well-defined authority and with meaningful guardrails. 

Professor Nevitt anchored the conversation in the Posse Comitatus Act (18 U.S.C. § 1385), a Reconstruction-era criminal statute that generally prohibits federal military forces—Army, Navy, Air Force, Marines (and now Space Force under Title 10)—from engaging in law enforcement activities such as arresting, searching, detaining, or seizing people, unless a clear exception applies. He emphasized that the Act does not apply to state-controlled National Guard forces, which operate under distinct legal authorities. 

From there, the conversation mapped the key exceptions and adjacent authorities that can bring the military into domestic contexts: 

First: The Insurrection Act (dating to the 1790s, with major revisions in the 19th century) allows the President—sometimes at a governor’s request, sometimes unilaterally—to deploy federal troops to address rebellion, obstructed enforcement of federal law, or related crises. While the authority has been used to enforce civil rights (including during desegregation), the speakers stressed that the statute’s language is old and broad, raising recurring questions about triggers, limits, and judicial review (with the classic case Martin v. Mott often cited as a deferential framework). 

And second: Article II “protective power” was discussed as a non-statutory, constitutional basis the executive branch has invoked to protect federal property and federal personnel, without invoking the Insurrection Act. Professor Nevitt described it as legally “murky” but increasingly relevant in modern flashpoint situations where federal facilities become focal points for protests or unrest. 

A central theme was the practical danger of mission mismatch: service members are trained for battlefield “rules of engagement,” not the civilian “rules for use of force” that govern policing. Professor Nevitt illustrated how small misunderstandings in terminology or posture can escalate quickly, underscoring why domestic deployments demand careful legal framing, clear operational constraints, and robust training. 

The second half of the event turned to “hot topics,” including the legal line-drawing problems raised when federal forces operate near immigration enforcement activity, the broader “blurring” between military and civilian policing (including through equipment transfers and the growing paramilitary appearance of some enforcement operations), and the evolving role of the National Guard. The speakers also discussed how the Guard is routinely activated for emergencies and disaster response, often successfully under Title 32, while noting that Guardsmen are heavily tasked and frequently balancing military obligations with civilian careers. 

The Q&A ranged from January 6 and the D.C. National Guard’s unusual chain of command, to the legal consequences of unlawful orders, to accountability questions under Posse Comitatus. Professor Nevitt emphasized the military’s long-standing internal principle: orders carry a strong presumption of legality, but “manifestly illegal” orders must not be followed, and lawyers (including JAGs) play a key role in enforcing that boundary. 

The conversation closed with a forward-looking concern: even when actions are technically lawful, repeated “non-traditional” domestic uses of the military can erode public trust and weaken norms that protect civilian governance. The speakers encouraged students to treat this area as one where statutory text, constitutional structure, and institutional tradition all matter, and where the stakes are high regardless of politics. 

Thank you to Professors Nevitt and Markovitch for an engaging discussion, and to everyone who joined and contributed thoughtful questions.