A union of administrative law judges on Monday sued over the constitutionality of President Donald Trump’s appointees to a federal labor panel, arguing the members should have been approved by the Senate, and therefore, their rulings should be thrown out.

In a complaint filed by Gupta Wessler attorneys, including Deepak Gupta, the Association of Administrative Law Judges allege the 10 current members of the Federal Service Impasses Panel—a group of presidential appointees that can resolve gridlocked labor disputes between a federal agency and its employees—should not have been allowed to issue a ruling last week that implemented the union’s new contract.