Supreme Court Justice Neil Gorsuch remained silent during the court’s oral arguments Monday in the case Janus v. American Federation of State, County and Municipal Employees, leaving unclear what he thinks about a major case involving public employee unions’ power to compel fees from non-members.

The newly appointed justice is the only member of the bench whose position on the issue is unknown, as the other justices split 4-4 on a nearly identical case last year.