Amici argue deployment of federal troops in California was a misuse of U.S. forces and threat to the constitutional rights of ordinary Americans

Penn’s Center for Ethics and the Rule of Law (CERL), the National Institute of Military Justice (NIMJ), Lawyers Defending American Democracy (LDAD), and Professors Claire Finkelstein, Brenner Fissell, and Mitt Regan have filed a motion to submit an amicus brief in the case Newsom v. Trump, supporting claims by Governor Gavin Newsom and the State of California that President Donald Trump exceeded his authority in federalizing the National Guard to suppress protests in Los Angeles.  

The amicus brief asserts that the deployment of federal troops to California violated two principles of democratic governance: federalism, which grants states primary control over their National Guard units, and the Posse Comitatus Act, a 147-year-old law prohibiting military involvement in civilian law enforcement, except in extreme circumstances.

“Federal case law underscores the need for vigilance in reviewing the lawfulness of federal executive action under circumstances that call these two core values into play,” according to the brief. “While the federal judiciary has repeatedly stressed the need for judicial deference in matters involving Commander-in-Chief authority and use of the U.S. military in protecting the country against foreign threats, domestic deployment of military forces, particularly when the mission touches on the rights of U.S. persons, raises a wholly different set of concerns.”

The amicus brief emphasizes that in deploying federal troops to California under these circumstances, the federal government put at risk the First and Fourth Amendment rights of Californians, and that courts should not show deference to the executive branch where constitutional rights are at issue.

“It is a fundamental responsibility, if not the fundamental responsibility, of Article III courts to protect the rights of American citizens and lawful residents against governmental overreach, including the potential for executive overreach in the exercise of presidential Article II authority,” the brief states.

“California’s case against the Trump administration for its deployment of the National Guard constitutes a critical defense of the autonomy of state government as a defender of U.S. democracy,” said Professor Finkelstein, faculty director of CERL and law professor at Penn. “The use of federal troops to suppress civil dissent in the absence of any true emergency violates both the important principle of federalism as well as the long-standing tradition of posse comitatus, which distinguishes military operations from civilian law-enforcement functions. Blurring the civilian-military divide imperils military readiness and leaves Americans vulnerable to violations of their constitutional rights.”

“Domestic use of the military is something the Framers fought a Revolution to prevent,” said Professor Fissell, vice president of NIMJ and law professor at Villanova. “While federal troops can legally ‘protect’ federal assets, this is not a blank check.”

“Core principles of democracy and the rule of law require that the executive branch not be able to enlist the military in performing functions that state law enforcement personnel can perform,” said Professor Regan, law professor at Georgetown. “This is crucial in preventing use of the military to suppress opposition to government policies and to infringe on core constitutional protection against unlawful detention and the use of force.”

A three-day federal trial for the lawsuit concluded on Wednesday, August 13, 2025.

About CERL

The Center for Ethics and the Rule of Law (CERL) is a non-partisan interdisciplinary institute at the University of Pennsylvania dedicated to preserving and promoting ethics and the rule of law in national security, warfare, and democratic governance. CERL draws from the study of law, philosophy, and ethics to answer the difficult questions that arise in domestic and transnational crises and conflicts.

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About NIMJ

The National Institute of Military Justice (NIMJ) is a private non-profit organization, founded in 1991, and dedicated to the fair administration of justice in the armed forces and improved public understanding of military justice. NIMJ’s leadership includes former judge advocates, private practitioners, and legal scholars.

About LDAD

Founded in 2019, Lawyers Defending American Democracy (LDAD) is a 501(c)(3) organization dedicated to the protection of the rule of law, the Constitution, and democracy. LDAD’s work includes authoring Calls-to-Action, research reports, amicus briefs, and articles calling for adherence to the rule of law and encouraging the legal profession and the public to join in speaking out against threats to the norms, freedoms, and principles of our democratic institutions.

About Claire Finkelstein

Claire Finkelstein is the Algernon Biddle Professor of Law and Professor of Philosophy at the University of Pennsylvania and the Founder and Faculty Director of its Center for Ethics and the Rule of Law (CERL). She is a Senior Fellow at the Foreign Policy Research Institute (FPRI) and the co-editor of The Oxford Series in Ethics, National Security and the Rule of Law. She is a widely published author in criminal law, national security, military law, and democratic governance and a sought-after opinion writer and commentator in prominent news outlets including the New York Times, Washington Post, The Hill, Lawfare and others in the United States and abroad.

About Brenner Fissell

Brenner M. Fissell is Professor of Law at Villanova University, and the former Class of 1964 Fellow at the U.S. Naval Academy. He served as an attorney-advisor for Chief Judge Scott Stucky of the U.S. Court of Appeals for the Armed Forces and as appellate defense counsel at the Guantanamo Bay Military Commissions. He is the Vice President of the National Institute for Military Justice (NIMJ) and a widely recognized expert in the Law of Armed Conflict (LOAC) and military law more generally.

About Mitt Regan

Mitt Regan is McDevitt Professor of Jurisprudence, Director of the Center on Ethics and the Legal Profession, and Coordinator of the Program on Law, Ethics, and International Security at Georgetown University Law Center. His work focuses on international law, national security, international human rights, legal ethics, military ethics, the legal profession and the rule of law, and ethical issues relating to artificial intelligence.  His books and articles focus on legal and ethical issues related to armed conflict, counterterrorism, the U.S. drone strike campaign, intelligence operations, and law firm practice.