The Supreme Court held 5-4 in Janus v. AFSCME that state statutes allowing public sector employers and unions to agree that employees who don’t join the union must still pay their “fair share” of collective bargaining costs violate the First Amendment. The Court also held that employees must “affirmatively consent” to join the union. More than 20 states authorize “fair share” for public sector employees.
In Abood v. Detroit Board of Education (1977) the Supreme Court held that the First Amendment does not prevent “agency shop” arrangements where public employees who do not join the union are still required to pay their “fair share” of union dues for collective-bargaining, contract administration, and grievance-adjustment. In Janus, the Supreme Court overruled Abood.