A federal judge made an important decision on September 16, allowing the cities of Fullerton, Costa Mesa, Goleta, and Santa Paula to weigh in on a lawsuit challenging how immigration stops are carried out in Southern California. U.S. District Judge Maame Ewusi-Mensah Frimpong granted these cities permission to file a friend-of-the-court brief, which is a document that offers additional information for the court to consider. The judge said the federal government did not oppose the filing.

The brief supports a request for a temporary order, or preliminary injunction, in Vasquez Perdomo v. Mullin. This case seeks to stop immigration stops that are based solely on race or ethnicity, which the plaintiffs argue violate the Fourth Amendment and equal protection rights. The lawsuit was originally filed against former Secretary of Homeland Security Kristi Noem but has now been updated to include Markwayne Mullin, who took over her position.

The cities filed their request on August 24 through Krista MacNevin Jee, a Fullerton lawyer. They emphasized that their diverse communities are directly impacted by the immigration enforcement mentioned in the lawsuit. Residents have reported serious concerns, including threats to constitutional rights and effects on local government operations. The cities made it clear they were not trying to repeat the original plaintiffs’ arguments, but to highlight the importance of the legal issues and their own community experiences.

The proposed brief contains 3,342 words, and the court has scheduled a hearing on the request for September 24 at 10 am in downtown Los Angeles. However, as of October 7, no public ruling had been issued on this issue.

This development comes more than a year after the Fullerton City Council initially voted on August 19, 2025, to support the lawsuit through an amicus brief, a supportive document filed in a court case. After gathering public comments in favor of this move, the brief had stalled. In January 2026, Fullerton’s city attorney, Baron J. Bettenhausen, explained that the case had to wait for further developments in court before they could move forward with their brief.

The case itself began on July 2, 2025, when five individuals, who had been stopped or arrested during immigration raids, filed a class-action lawsuit alongside several advocacy groups. Other cities, including Los Angeles and Long Beach, later joined as intervenors. In July 2025, Judge Frimpong issued temporary orders prohibiting stops based solely on race, language, location, or type of work, but the U.S. Supreme Court lifted those restrictions in September 2025. On February 19, 2026, the judge allowed the case to continue, rejecting the federal government’s attempts to dismiss it.

Key Dates:

– July 2, 2025: Lawsuit filed.
– July 11, 2025: Court issues temporary restraining orders.
– August 19, 2025: Fullerton City Council votes to file an amicus brief.
– September 8, 2025: Supreme Court lifts restrictions on stops
– November 13, 2025: Court grants a preliminary injunction on a separate claim.
– January 28, 2026: Fullerton’s counsel says no pending matter for a brief
– February 19, 2026: Court denies the government’s motions to dismiss.
– July 27, 2026: Plaintiffs file a new injunction motion regarding stops and equal protection.
– August 24, 2026: Fullerton, Costa Mesa, Goleta, and Santa Paula request leave to file an amicus brief.
– September 16, 2026: Frimpong grants four cities leave to file an amicus brief.
– September 24, 2026: Hearing on the injunction motion scheduled.