A federal court judge in California ruled last Thursday that the Los Angeles County Sheriff’s Department violated the constitutional rights of thousands of inmates that the agency detained for federal immigration authorities without probable cause, the latest in a series of legal blows to a strategy that forms the linchpin of the Trump administration’s crackdown on illegal immigration.   

U.S. District Judge Andre Birotte Jr. held the LA Sheriff’s Department liable for violating the Fourth Amendment rights of inmates the agency held without probable cause for U.S. Immigration and Customs Enforcement (ICE) through the use of detainers, requests to hold inmates for up to 48 hours past their release date so that ICE can take those individuals into custody.  

“The court’s decision vindicates years of work by the Los Angeles immigrant community to challenge the Sheriff’s Department’s abuses and throws a major wrench in the Trump administration’s deportation machine,” said Jessica Bansal, litigation director at the National Day Laborer Organizing Network, in a statement from the ACLU of Southern California, one of five organizations that brought two lawsuits against the sheriff’s department and ICE.    

Birotte held that holding inmates beyond their release dates on the basis of immigration detainers constitutes a new arrest under the Fourth Amendment, and thus the Sherriff’s Department could only arrest those people if officers had probable cause to suspect that the individuals were involved in criminal activity. The department’s policy is now defunct. 

“The LASD officers did not have probable cause that the individuals were involved in criminal activity, but were instead holding these individuals on the basis of civil immigration detainers,” wrote Birotte in the decision. “The LASD officers have no authority to arrest individuals for civil immigration offenses, and thus, detaining individuals beyond their date for release violated the individuals’ Fourth Amendment rights.”

The decision mirrors federal court rulings over the past several years on ICE detainers that have found that the practice violates Fourth Amendment protections against unreasonable search and seizure. Last March, ICE issued a new policy requiring all detainers to be accompanied by an ICE administrative warrant.  

However, legal experts say the ICE “warrant” is problematic because it is an administrative document, not a judicial warrant, which are documents issued by a judge or magistrate, who use facts to determine probable cause to arrest a person.

An ICE “warrant” is still insufficient to put a person in jail, as Cody Wofsy, a staff attorney with the ACLU Immigrants’ Rights Project, explained to ThinkProgress in an investigation published in December. A local law enforcement agency must have a judicial warrant with probable cause to keep a person in custody; otherwise, local agencies run the risk of running afoul of the constitution, he said. 

By keeping people jailed past their release date — even if it’s done at the request of another agency, such as ICE — these law enforcement agencies risk lawsuits, such as the one settled in Virginia earlier this year by Henrico County Sheriff Michael Wade (R).

There, a Salvadoran immigrant sued after the Henrico Jail held him past his release date at ICE’s request. As a result of that case many Virginia sheriffs have stopped holding people in jail for ICE unless they get a warrant or order of detention signed by a federal judge or magistrate.

ICE itself requires its officers serve the ICE “warrant” in person, and inform the jailed person that they are under arrest for a civil violation, legal experts told ThinkProgress. Yet, many agencies don’t follow those guidelines and instead accept these documents from ICE via fax or email.

Last month, on the heels of a ThinkProgress investigation,  the Fairfax County Sheriff’s Office in Virginia announced it will no longer hold people in jail past their release date for ICE unless the request is accompanied by a court order, and it will cancel its controversial detention contract with federal immigration authorities.

However, other law enforcement agencies with similar contracts continue to hold people past their release date for ICE using the detainer request and administration warrant. The Alexandria Sheriff’s Office, in the city of Alexandria, VA, is one of those agencies, according to its policies posted online.

As the federal courts continue to scrutinize ICE “warrants” — and so far the courts have ruled against the practice on Fourth Amendment grounds — legal experts told ThinkProgress that they see the next legal battle crystallizing around local law enforcement agencies that use a combination of the ICE detainer, administration warrant, and federal detention contracts to house inmates in local jails.

Whether responding to ICE detainers or ICE “warrants,” local law enforcement agencies place themselves at risk of violating the constitution if they lack probable cause and legal authority to make the arrest, said Wofsy of the ACLU.

Based on the federal court’s decision in Los Angeles last Thursday, the plaintiffs may be entitled to monetary damages, according to the ACLU.

“This decision is a victory for the constitutional rights of both citizens and noncitizens alike who for years have been subject to unlawful arrest and detention due to ICE’s immigration requests,” Jennie Pasquarella, director of immigrants’ rights and senior staff attorney for the ACLU of Southern California, said in a statement. “As the highly polemical ‘sanctuary city’ debate continues, this decision further clarifies that the immigration detainers at the heart of that debate are unlawful and that police who honor them violate the constitution.”