A federal judge ruled on Thursday to block Philadelphia from enforcing a ban on federal officers wearing masks while they are on duty. 

This temporary ruling was in response to a lawsuit filed against the city by the Department of Justice, which argued that the ordinance was a “blatantly unconstitutional” effort to regulate the conduct of federal agents and would “endanger officers and reduce operational effectiveness,” according to The Hill. 

Federal Judge Chad Kenney ruled that the DOJ was likely to succeed in its challenge, and thus barred Philadelphia from implementing or enforcing the law against federal agencies and officers during the period that legal proceedings play out.

“When the Philadelphia City Council voted to pass Bill No. 260060 … it attempted to sidestep the Constitution’s clear mandate and disregarded this fundamental principle of law that has informed American jurisprudence for over 200 years,” the judge wrote in the 30-page order. 

The “Constitution’s clear mandate” he was referring to is the Constitution’s Supremacy Clause.  

“Today, the court blocked Philadelphia’s unlawful attempt to regulate federal law enforcement,” a DOJ spokesperson told The Hill in a statement. “The Department of Justice will keep fighting jurisdictions that try to obstruct President Trump’s immigration enforcement with policies that endanger agents and public safety.”