U.S. District Judge Maame Ewusi-Mensah Frimpong has blocked immigration officers across seven Southern California counties from making warrantless civil immigration arrests unless they first determine, based on the totality of the circumstances known to the officer, that the person is likely to escape before a warrant can be obtained. The preliminary injunction was issued under seal in early September and unsealed Wednesday in the Central District of California, where it will govern arrests in Los Angeles, Orange, Riverside, San Bernardino, Ventura, Santa Barbara, and San Luis Obispo counties.

The order grew out of Vasquez Perdomo v. Noem, a challenge brought by the ACLU of Southern California, Public Counsel, and Los Angeles based immigrant advocacy groups to enforcement practices that escalated during the sweep campaigns of the past year. What makes the ruling notable is less the legal standard, which federal courts in other districts have applied before, than the evidentiary record behind it: the court found that the documents meant to justify warrantless arrests were frequently missing, canned, or at odds with what body cameras recorded.

The paperwork was the problem

The plaintiffs reviewed 113 arrest records from the region and found that nearly 80 percent contained either no escape-risk assessment at all or language so generic it could have been pasted into any file. That finding became the spine of the court's analysis. Under long-standing immigration authority, an officer may arrest someone without a warrant when the officer has reason to believe the person is present in violation of the law and likely to escape before a warrant can be obtained. The second element is supposed to be an individualized judgment.

Judge Frimpong held that mere unlawful presence does not, by itself, satisfy the escape-risk element. Officers must document probable cause and the "specific, particularized facts" supporting their pre-arrest conclusion that the person would flee. A bare assertion that someone is removable does not carry that load.

The practical effect is that the assessment moves from an afterthought to the controlling document of the arrest. If the facts do not support flight risk, the arrest does not happen, or it happens only after a warrant is obtained.

What the videos showed

The evidentiary record included body-camera and surveillance footage that contradicted written narratives in at least one cited case. According to court findings, officers described a person as "running away" when video showed the man walking normally and texting. The court's willingness to weigh the video against the paperwork did something important to the credibility of the enforcement record as a whole: a handful of documented discrepancies casts doubt on files that were never tested.

This is where the ruling connects to its remedy. Judge Frimpong did not simply tell officers to try harder. She ordered documentation of the specific facts behind every warrantless arrest, which is the mechanism that makes the assessment reviewable in the first place. A rule without a record is not enforceable by anyone outside the arrest itself.

The memo the court barred

The court also prohibited officers from relying on a January 2026 memorandum by Todd Lyons, the former acting director of Immigration and Customs Enforcement, which plaintiffs argued treated undocumented status alone as sufficient evidence of flight risk. Barring reliance on the memo matters because internal guidance often survives litigation of the underlying policy: an injunction against practices can be evaded by pointing to the memo as the practice.

By naming the memo and taking it out of circulation for these arrests, the court cut off the most direct route back to the status quo. Officers cannot say the memo told them to do what the injunction forbids.

What the government argued

Justice Department attorney Daniel Mummolo argued during the proceedings that no warrantless arrest policy existed, "either in written or unwritten form." The government also asked the court to stay its order for 14 days while an appeal was considered.

Judge Frimpong denied the stay in direct language. The government, she wrote, "cannot reasonably assert that it is harmed in any legally cognizable sense" by being ordered to follow the law. That sentence reflects the structure of the litigation: the government's position was not that the practices were defensible on their own terms, but that they were not practices at all, just individual judgments made in the field. The court answered that a thousand individual judgments with the same gaps amount to a pattern, whether or not anyone wrote the pattern down.

The Associated Press reported that the Department of Homeland Security did not immediately respond to requests for comment.

A class action with a long memory

The court certified a class covering people arrested since June 6, 2025, without a warrant and without an individualized escape-risk assessment. The class-certification date reaches back more than a year, which gives the litigation its retrospective sweep: the case is not only about how arrests will happen from now on, but about what happened to a class of people during the period when the challenged practices were at their peak.

The ruling also joins a growing line of similar decisions. Federal judges in Portland, Colorado, Washington, D.C., and the Eastern District of California have blocked comparable warrantless-arrest practices. Some of those courts later found that agents continued the conduct anyway, which is why the documentation requirement and the named ban on the Lyons memo carry weight: they give monitors something to check.

ACLU attorney Mayra Joachín said the order should put an end to hundreds of unlawful arrests in the region, and said the groups would monitor compliance. Whether the record-keeping requirement actually disciplines the field is now the open question, and it will be answered not in another hearing but in the files officers write.

Where the escape-risk standard comes from

The standard Judge Frimpong applied is older than the current enforcement debate. Federal law has long permitted warrantless immigration arrests in limited circumstances, and the courts have read the flight-risk element as requiring something more than the fact of unauthorized presence. The Ninth Circuit, which oversees the Central District of California, has recognized the escape-risk requirement in cases going back decades. What changed in the last year is the scale at which officers were making warrantless arrests, which is what moved the question from appellate doctrine to a class action over thousands of encounters.

The ruling is best understood as a re-anchoring rather than an invention. The judge did not create a new requirement. She held that the existing requirement means what it says, and that a record missing the required finding is a record of an arrest that should not have happened without a warrant. The practical consequence is procedural: agents who want to arrest without a warrant now need the warrant process to be the fallback, not the exception. A warrant requires a magistrate's signature, and a magistrate requires the same particularized showing the injunction requires in the field.

What compliance will look like

The injunction gives the plaintiffs' organizations something specific to monitor, which is what distinguishes it from the general statements of policy the government insisted were the only thing on paper. The documentation requirement means every warrantless arrest in the seven counties now produces a written flight-risk assessment that can be checked against the facts later. The ban on the Lyons memo means officers cannot point to headquarters guidance to justify the old practice.

Whether the order sticks will be tested in the ordinary course of enforcement. The court denied a stay, but the government can appeal, and appellate review of preliminary injunctions in this posture moves on a different timeline than the arrests themselves. In the meantime, the order is the law of the district, and the agencies that operate in it have a choice: obtain warrants, document genuine flight risk, or wait for the appeal.

The deeper question the case poses has nothing to do with procedure. It is whether a documentation requirement can discipline a field practice, or whether the paperwork will simply be filled in to match the arrest the officer already decided to make. The video evidence in this case suggests the pre-existing paperwork sometimes did exactly that, describing people as fleeing who were walking. The injunction cannot make officers honest. It can make their claims specific, dated, and checkable, which is what a court can do, and it has done it.

The ruling also leaves the warrant path fully intact, and that is worth stating plainly. Nothing in the injunction prevents agents from presenting their probable cause and flight-risk evidence to a magistrate and arresting on a judicial warrant. The order's logic is that the warrant process exists for exactly this purpose, and that the volume of warrantless arrests had turned the exception into the rule. For the people the order protects, the difference between the two paths is not theoretical: a magistrate's review happens before the arrest, in a neutral setting, on a written record. The injunction moves Southern California enforcement back toward that path, and it will be possible to measure, in the arrest records that follow, whether it stayed there.

The injunction does not end enforcement. It sets the evidentiary price of warrantless enforcement, and puts the receipt in the file where a judge, and eventually the public, can read it.

Primary sources

  1. LA Times for the unsealed injunction, its geographic scope, and the stay denial.
  2. AP News for the class certification details, the 113-record review, and agency response.
  3. CalMatters for the litigation background and the video evidence contradicting officer narratives.