The Supreme Court denied the Trump administration’s request to deploy National Guard troops to the Chicago area amid escalating protests over federal immigration enforcement operations. The 6-3 decision marks the first time the high court has addressed the issue of military deployments for domestic law enforcement and establishes limits on presidential authority to federalize state troops.

The unsigned majority opinion concluded that “at this preliminary stage, the Government has failed to identify a source of authority that would allow the military to execute the laws in Illinois,” leaving in place lower court orders that bar the deployment while permitting the federalized troops to remain under federal control.

The case came before the court shortly after President Trump’s October 4 decision to call 300 members of the Illinois National Guard into active federal service to protect federal personnel and property in Chicago, particularly around an Immigration and Customs Enforcement processing facility in Broadview.

The following day, 200 members of the Texas National Guard were also federalized and sent to Chicago.

Illinois and Chicago had challenged the deployment, arguing that Trump had “ulterior motives aimed at punishing his political adversaries” and that his actions violated the Tenth Amendment and the Posse Comitatus Act. U.S. District Judge April Perry issued a temporary restraining order on October 9, stating she saw “no credible evidence that there is a danger of rebellion.” The Seventh Circuit largely upheld Perry’s order, though it modified it to allow federalization without deployment.

According to the government, federal immigration enforcement efforts have encountered “significant resistance, as well as some violence” in Chicago. The administration alleged that ICE officers have been “obstructed, threatened, and assaulted” while attempting to perform their duties, and that the Broadview facility has been the site of “frequent and sometimes violent protests, damaging federal property and threatening the safety of federal officers.”​

The deployment came as part of “Operation Midway Blitz,” a federal immigration enforcement campaign that resulted in over 1,000 arrests in Illinois between September 8 and October 3, according to the Department of Homeland Security. The intensified enforcement sparked near-constant protests at the Broadview facility, located approximately 12 miles west of Chicago.

Illinois Governor J.B. Pritzker strongly opposed the deployment, stating that federal officials gave him an ultimatum Saturday morning to either activate the Illinois National Guard voluntarily or have the Trump administration take command of state troops over his objections.

The Supreme Court’s majority opinion centered on the interpretation of 10 U.S.C. §12406(3), the federal statute the President invoked to federalize the Guard. This provision empowers the president to call forth the National Guard if he is “unable with the regular forces to execute the laws of the United States.”​

The Court concluded that the term “regular forces” in this statute “likely refers to the regular forces of the United States military,” not civilian federal law enforcement officers as the government had argued. This interpretation carries significant implications: to call the Guard into active federal service under this provision, the president must be “unable” with the regular military “to execute the laws of the United States.”​

The majority opinion further reasoned that because the statute requires an assessment of the military’s ability to execute the laws, it “likely applies only where the military could legally execute the laws.” Such circumstances are exceptional under the Posse Comitatus Act, which prohibits the military from “executing the laws” except in cases expressly authorized by the Constitution or an Act of Congress.

“So before the President can federalize the Guard under §12406(3), he likely must have statutory or constitutional authority to execute the laws with the regular military and must be ‘unable’ with those forces to perform that function,” the Court wrote.

The Court found that the government failed to meet this threshold. While the President relied on inherent constitutional authority to use the military to protect federal personnel and property, the government also maintained—consistent with longstanding executive branch views—that performing such protective functions does not constitute “executing the laws” within the meaning of the Posse Comitatus Act.​

“If that is correct, it is hard to see how performing those functions could constitute ‘executing the laws’ under §12406(3),” the Court reasoned, citing the principle that Congress does not lightly attach different meanings to the same term in related statutes.​

The majority emphasized that its decision comes at a “preliminary stage” and does not address “the reviewability of findings made by the President under §12406(3) or any other statute.”

Justice Brett Kavanaugh, joined by no other justices, agreed with denying the stay but argued the Court should have done so on narrower grounds.​

While Kavanaugh concurred that “regular forces” likely means the U.S. military rather than civilian law enforcement officers, he would have decided the case simply on the ground that “it does not appear that the President has yet made the statutorily required determination that he is ‘unable’ with the U.S. military, as distinct from federal civilian law enforcement officers, to ensure the execution of federal law in Illinois.”​

“On that narrow ground, I would deny the Government’s application for a stay,” Kavanaugh wrote. “We need not decide more, so I would not decide more.”

The justice also expressed concern about the Court’s process, suggesting that before addressing “challenging and far-reaching statutory questions,” the Court should have “at least invited further briefing and possibly also held oral argument, either on the application itself or by granting certiorari before judgment.” He cited recent cases where the Court employed such additional procedures when dealing with applications of substantial import.​

Kavanaugh noted in a footnote that the Court’s opinion “does not address or purport to disturb the President’s long-asserted Article II authority to use the U.S. military (as distinct from the National Guard) to protect federal personnel and property.” He suggested one consequence of the Court’s ruling is that “it could cause the President to use the U.S. military more than the National Guard to protect federal personnel and property in the United States.”

Justice Samuel Alito criticized the Court for abandoning the principle of party presentation by raising an argument that respondents had waived three times in lower courts. Both parties originally agreed that “regular forces” meant civilian federal law enforcement officers, not military personnel, but the Supreme Court ordered a new briefing on this question, and respondents then switched positions.

Alito argued the Court should have decided the case based on the parties’ original arguments about whether civilian officers were actually able to execute federal law in Chicago. He documented substantial evidence of violence: over 30 injured federal officers, organized rioters with weapons blocking the ICE facility, officers being rammed by vehicles, death threats and bounties placed on officers, and local police refusing to respond to emergency calls. The majority and Judge Perry found these declarations “unreliable.”

The dissent also challenged the majority’s statutory interpretation, questioning whether the Posse Comitatus Act limits inherent presidential authority and arguing that excluding “protective functions” from “executing the laws” would paradoxically allow Guard members to arrest aliens but not protect officers from lethal attacks.​

Justice Neil Gorsuch wrote about the need for judicial restraint given the “sensitive and gravely consequential questions” the case presented about the National Guard and military roles in domestic law enforcement. He outlined numerous unresolved fundamental issues: whether the president must be unable to execute laws with civilian law enforcement or military troops; whether and under what standard presidential declarations are judicially reviewable; how §12406(3) interacts with the Posse Comitatus Act and Insurrection Act; what inherent Article II power exists; and the gravest question of all—when, if ever, may the federal government deploy the professional military for domestic law enforcement consistent with the Constitution.

Like Alito, Gorsuch would have decided the case narrowly based on the premise both parties originally presented. However, he explicitly refused to venture opinions on the broader constitutional and statutory questions, stating they deserve “the full airing they so clearly deserve” in a future case where they are properly preserved and fully briefed.​

The ACLU of Illinois responded to the ruling, stating, “The Court’s ruling cuts through the Administration’s manufactured rationale for sending National Guard troops into the Chicagoland area,” said Kevin Fee, Legal Director of the ACLU of Illinois. “As the District Court and Court of Appeals for the Seventh Circuit made clear, the Administration has no coherent fact-based justification to deploy these forces. The Administration’s account of the conditions on the ground in Chicagoland is pure fantasy.”