Washington (CNN) A federal judge is preparing to hear arguments about whether federal employees should be limited in discussing the ongoing impeachment trial of President Donald Trump.

A major federal employees union filed last week for a preliminary injunction against government-wide guidance issued in 2018 that prohibits federal employees from sharing their opinions about the President's impeachment.

A federal judge has scheduled a telephone conference Wednesday morning to set a schedule for the union and government to file documents and make their arguments.

The American Federation of Government Employees argued the Office of Special Counsel's "policy is unconstitutionally overbroad and viewpoint discriminatory."

It said the restrictions extend beyond the limits of the Hatch Act, which prohibits federal employees from discussing candidates in an upcoming election while on the job, and have not been enforced "against numerous Administration officials who have brazenly violated it by advocating against the President's impeachment, or by denigrating the 'resistance.'" The union also said some of the restrictions appear to apply when employees are off the clock.

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