A federal judge on Thursday blocked President Donald Trump’s broad executive actions aimed at dismantling the Department of Education, ruling that such moves require congressional authorization.

U.S. District Judge Myong Joun of Massachusetts also issued a preliminary injunction ordering the Trump administration to reinstate employees who were dismissed in mass layoffs earlier this year. The administration has pledged to appeal the ruling.

“It is only reasonable to expect that an RIF [reduction in force] of this magnitude will likely cripple the Department. The idea that Defendants’ actions are merely a ‘reorganization’ is plainly not true,” Joun, a Biden appointee, wrote in his opinion.

Trump signed an executive order in March to begin winding down operations at the Education Department.

Before the court’s intervention, Education Secretary Linda McMahon had moved to lay off more than 1,300 employees. Combined with roughly 600 voluntary departures, the cuts reduced the Department of Education’s workforce by about half, from its original size of approximately 4,000, the New York Post reported.

While publicly signaling an intent to eliminate the department, the Trump administration argued in court filings that the mass terminations were simply an administrative measure aimed at improving government efficiency—an action it claimed fell within the secretary’s legal authority.

“Defendants do acknowledge, as they must, that the Department cannot be shut down without Congress’s approval, yet they simultaneously claim that their legislative goals … are distinct from their administrative goals (improving efficiency),” added Joun. “There is nothing in the record to support these contradictory positions.”