The 9th U.S. Circuit Court of Appeals in a 2-1 decision in SEIU Local 121RN v. Los Robles Regional Medical Cente, ruled on 18 September 2020 that the standard for evaluating whether the courts or the arbitrators themselves must decide if commercial disputes are to be arbitrated is equally applicable in the context of labor disputes. The 9th Circuit stated that its previous decision to the contrary in United Brotherhood of Carpenters v. Desert Palace Inc. in 1996 had been overruled by more recent U.S. Supreme Court precedent in Granite Rock Co v. International Brotherhood of Teamsters.
The 9th Circuit held that since the collective bargaining agreement between Los Robles Regional Medical Center in California and a local union representing its nurses, Service Employees International Union (SEIU), did not specify who must determine that threshold issue, it must be ruled upon by a court.
For more information see here.
For the complete judgment see here.