The United States Supreme Court has held that an application of state law is preempted by section 301 of the Labor Management Relations Act only if such application requires interpretation of a collective bargaining agreement.
Lingle v. Norge Division, Magic Chef, Inc., 108 S. Ct. 1877 (1988).
Labor Law - Labor Management Relations Act - Preemption,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol27/iss4/10