The Supreme Court found for Janus in Janus v. AFSCME.
I do want to point out one thing that I think many people are going to get wrong on this: this was about AGENCY FEES, not dues. The case was brought by someone who disagreed with the political positions taken by the union which represented him and did not wish to contribute to support for those political positions. What he was being charged, however, was not dues--he was paying only for the representation he got at the bargaining table by the union.
Currently, unions are required to represent all those of a unit at the table, whether or not they are members of the union (this is "exclusive representation"). The union charges non-members for this service. There's some discussion online about a suggestion from Justice Alito's writing that states could allow unions to refuse to represent non-members.