The US Supreme Court Friday unanimously ruled in favor of the FBI in Federal Bureau of Investigation v. Fazaga, holding that the state secrets privilege used to block the disclosure of information that the government finds harmful to national security is not displaced by the Foreign Intelligence Surveillance Act (FISA).

The lawsuit was filed in 2011 by three Muslim men who alleged the FBI conducted improper surveillance on a set of mosques in 2006 and 2007. The men claim they were targeted by the federal government and the Southern California community for surveillance because of their religion.

The FBI insisted that disclosing information sought by the three men would harm national security interests. The district court dismissed the lawsuit on the basis of state secrets privilege, which permits dismissal if the litigation would require disclosure of information that would harm national security.

The US Court of Appeals for the Ninth Circuit reversed the district court’s decision in part in 2019. The court held that the FISA, a federal law regulating government surveillance, trumped the state secrets privilege asserted by the government.

On Friday, the Supreme Court reversed and remanded the Ninth Circuit’s decision in a 9-0 ruling. Justice Alito wrote the opinion, explaining that the FISA provision “does not displace the state secrets privilege.” As he wrote: “FISA makes no reference to the state secrets privilege. It neither mentions the privilege by name nor uses any identifiable synonym, and its only reference to the subject of privilege reflects a desire to avoid the alteration of privilege law.”

Because the Supreme Court reversed and remanded the case, it will return to the lower court for further litigation.