The Supreme Court of the United States has held that prior to ERISA, a state's power to regulate pension plans by imposing minimum vesting and funding requirements more stringent than those contained in a collective bargaining agreement was not preempted by federal labor policy.
Malone v. White Motor Corporation, 435 U.S. 497 (1978).
James P. Hollihan,
Labor Law - Federal Preemption - Pension and Retirement Plans,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol17/iss1/17