A federal judge issued a ruling Friday ordering a temporary pause in the Trump administration’s plan to slash various agencies and fire tens of thousands of federal workers. 

U.S. District Judge Susan Illston of California issued a two-week pause, arguing that while the president can institute changes to federal agencies and conduct mass layoffs, he has to perform them in “lawful ways.” 

“The President has the authority to seek changes to executive branch agencies, but he must do so in lawful ways and, in the case of large-scale reorganizations, with the cooperation of the legislative branch. Many presidents have sought this cooperation before; many iterations of Congress have provided it,” Illston said in a 42-page order. 

“Nothing prevents the President from requesting this cooperation—as he did in his prior term of office. Indeed, the Court holds the President likely must request Congressional cooperation to order the changes he seeks, and thus issues a temporary restraining order to pause large-scale reductions in force in the meantime,” the federal judge said Friday. 

The judge’s restraining order will last until May 23, during which period new reduction-in-force notifications from the Office of Management and Budget and the Office of Personnel Management will not go into effect. 

The ruling comes in response to a lawsuit filed last month by various labor unions, cities, nonprofits and counties, marking one of the biggest challenges to Trump’s executive actions yet. The plaintiffs contended that the president does not have the authority to retool the federal government without the green light of Congress. 

A number of agencies are covered under the Friday order, including the Department of Labor, Energy, Commerce, Veterans Affairs, Health and Human Services, and others. 

Tens of thousands of federal workers have been fired, and several federal agencies have seen dramatic reductions or been shuttered in recent months. Trump, with the help of Elon Musk and his Department of Government Efficiency, has worked to shrink the federal government in his second term, sparking legal action.

In response to recent lawsuits, several judges have ordered pauses in the Trump administration’s sweeping efforts.