A Test of Limits: Posse Comitatus and the National Guard

OPINION — “At the June 7, [2025] briefing, [Army North’s Contingency Command Post Deputy Chief of Staff] Mr. [William] Harrington stated — based on his experience and training within the Department of Defense — ‘if any National Guard troops were federalized as part of the deployment [to Los Angeles], they would lose the ability to conduct law enforcement activities because of the Posse Comitatus Act.’…Among other instructions, Task Force 51[the California National Guard contingent of] troops were told that they could not impede vehicle or pedestrian traffic or block public roads, because these are law enforcement functions.”

That is an excerpt from the 52-page opinion of United States District Judge Charles R. Breyer in a case brought by California Governor Gavin Newsom, who objected to the Trump administration’s federalization of elements of his state’s National Guard. The opinion directly affected only 300 California National Guard troops remaining on duty, from the 4,000 originally called up.

On Wednesday, the Trump administration filed a notice to appeal the decision with the 9th U.S. Court of Appeals.

But Breyer’s opinion could have a nationwide impact if it survives appeals. That is because Trump’s original memorandum that called the California National Guard into federal service never specifically mentioned Los Angeles or California. To the contrary, as Breyer himself pointed out, “it instructed the Secretary of Defense ‘to coordinate with the Governors of the States and the National Guard Bureau in identifying and ordering into Federal service the appropriate members and units of the National Guard.’”

President Trump in the past has threatened to call up National Guard troops in Illinois, Maryland and other states with high crime rates and Democratic governors, but after Breyer’s opinion, Trump may be hesitating.

On Wednesday, during a meeting with Polish President Karol Nawrocki, Trump said, “Do we go to Chicago? Do we go to a place like New Orleans, where we have a great [Republican] governor, Jeff Landry, who wants us to come in and straighten out a very nice section of this country that’s become quite, you know, quite tough, quite bad.”

I will discuss below another legal issue involved in the case, but first I want to look at the Posse Comitatus violations mentioned above.

According to Breyer’s opinion, “Major General Scott Sherman, the deputy commanding general support for U.S. Army North and commander of Task Force 51, oversaw the training of Task Force 51. He testified [during Breyer’s court hearing] that his number two priority (after troops’ welfare and safety) was ‘to ensure that they followed the standing rules on the use of force exactly as was written.’ Accordingly, he ensured that Task Force 51 troops knew that ‘they weren’t allowed to do any law enforcement actions. Law enforcement had to do it themselves.’”

The Task Force 51 training slide shown Task Force 51 troops specified 12 law enforcement functions prohibited by the Posse Comitatus Act but, according to Breyer’s presentation of the facts, the troops “were orally instructed that the four functions listed in red—security patrols, traffic control, crowd control, and riot control—were subject to a so-called constitutional exception to the Posse Comitatus Act.”

This latter oral instruction, Breyer wrote, came “all the way from the top of [the Department of Defense] down to Task Force 51,” according to court testimony.

Although the latter instruction was initially not put in writing, Defense Secretary Pete Hegseth did so in a memorandum issued June 23, [2025] that explained the scope of the alleged constitutional exception to the Posse Comitatus Act.

Hegseth’s memorandum directed that “Task Force 51…may take reasonable measures to prevent the destruction or defacement of Federal Government property including crowd control, temporary detention, cursory search (such as safety-related searches for weapons incident to temporary detention), measures to ensure the safety of persons on the property, and the establishment of security perimeters reasonably necessary to protect the property,” according to Breyer’s opinion.

Breyer also wrote that the June 23, Hegseth memo, in a second bullet point, asserted “that wherever federal personnel go, Task Force 51 troops can accompany them and establish perimeter control, engage in crowd control, and otherwise perform any functions ‘necessary to ensure the execution of Federal functions and the safety of Federal personnel.’”

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The June 23 memo reminded me that this was not the first time I had heard that Hegseth appeared to tell troops they did not have to follow legal advice.

During a November 2024 interview with podcaster Shawn Ryan, Hegseth described that when he was an Army officer in Iraq in 2005, his platoon got a briefing from a military lawyer in Baghdad on the rules of engagement. Hegseth said the lawyer told him and his troops that they could not shoot someone carrying a rocket-propelled grenade unless it was pointed at them.

Hegseth then told Ryan, “I remember walking out of that briefing, pulling my platoon together and being like, ‘Guys, we’re not doing that. You know, like if you see an enemy…engage before he’s able to point his weapon at you and shoot, we’re going to have your back.’”

Breyer’s opinion also listed times when he believed the California Guard violated Posse Comitatus saying, “The record is replete with evidence that Task Force 51 executed domestic law in these prohibited ways. Task Force 51 set up traffic blockades on roads at a residential enforcement operation in Long Beach, as part of Operation Excalibur at MacArthur Park.”

Breyer said, “Operation Excalibur involved federal law enforcement officials marching across MacArthur Park while Task Force 51 remained stationed on the outside of the park in military vehicles—Humvees and tactical vehicles—including at two traffic control points to prevent vehicular traffic along a stretch of Wilshire Boulevard.”

Breyer also pointed out, “Despite the risk associated with Operation Excalibur and the numerous rehearsals, DHS [the Department of Homeland Security which ran Operation Excalibur] planned to give LAPD [Los Angeles Police Department] only two hours’ notice of the operation.” Breyer said that illustrated Trump administration officials “lack of cooperation with their state and local counterparts [which] raises red flags,” and highlighted “the lack of any showing by Defendants [Trump officials] that state and local officials were unable or unwilling to execute the laws.”

Beyond the factual violations of the Posse Comitatus Act, according to Breyer’s opinion, Trump officials argued that same Act, which authorizes the federalization of National Guard units could be applied “whenever… the President is unable with the regular forces to execute the laws of the United States.”

I should note here that the police power is the quintessential power that the Constitution reserves to the states. Local and state police are among the “regular forces to execute the laws” referred to above.

However, the Trump officials’ lawyers argued, “The [Posse Comitatus] Act does not even apply to the federalized National Guard,” because the Constitution’s so-called “Take Care” clause under Article II, Section 3 states, “he [the President] shall take Care that the Laws be faithfully executed.”

Breyer, in his opinion, pointed out, “the Court [Breyer] is unaware of any person—government lawyer, military or civilian official, court, or commentator—who has made this argument other than Defendants’ [Trump officials’] lawyers in this case.”

Breyer added that such an interpretation “would represent a marked shift in the balance of power between the Executive and the Legislature,” adding it “would create a loophole in the Posse Comitatus Act that would swallow the entire Act…[and] would place no meaningful guardrails on the federalization and use of National Guard troops.”

“If the President wants to avoid the Act’s restrictions,” Breyer said, “he must invoke a valid exception…along with its requisite showing that state and local law enforcement are unable or unwilling to act.”

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In concluding his opinion, Breyer wrote that Trump officials “are not required to withdraw the 300 National Guard troops currently stationed in Los Angeles, nor are they barred from using troops consistent with the Posse Comitatus Act…Thus, for example, federal troops can continue to protect federal property in a manner consistent with the Posse Comitatus Act.”

But Breyer ordered that the remaining Guard troops could not engage in “arrests, apprehensions, searches, seizures, security patrols, traffic control, crowd control, riot control, evidence collection, interrogation, or acting as informants, unless and until Defendants satisfy the requirements of a valid constitutional or statutory exception, as defined herein, to the Posse Comitatus Act.”

As noted above, Trump officials have appealed Breyer’s opinion to the 9th Circuit Court of Appeals. On Thursday, a 9th Circuit three-judge panel froze the situation until it could have a court session and hear arguments in greater detail.

This appears to be another situation – here the President’s use of federalized National Guard troops — where a Trump attempt to expand Presidential power may be headed to the Supreme Court.

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