In the case of The District of Columbia and Sharon Pratt Kelly, Mayor v. The Greater Washington Board of Trade in 1992, the U.S Supreme Court ruled on a dispute concerning an amendment to the Employee Retirement Income Security Act (ERISA). This amendment required that employers who provided health insurance for their employees must also provide equivalent coverage for mental health benefits. The Greater Washington Board of Trade argued that this law violated ERISA's preemption clause which prohibits states from enacting laws relating to any employee benefit plan covered by ERISA. However, the court disagreed with this argument stating that Congress intended to amend ERISA through its passage of legislation requiring parity in mental health benefits. Therefore, it was held that such provisions did not violate ERISA’s preemption clause as they were part and parcel of a comprehensive national scheme for employee benefit plans.

In the dissenting opinion for The District of Columbia and Sharon Pratt Kelly, Mayor v. The Greater Washington Board of Trade case in 1992, Justice Scalia argued that the majority's decision was inconsistent with previous interpretations of ERISA preemption clause. He believed that this inconsistency would create confusion among lower courts and potentially lead to arbitrary decisions about what state laws are preempted by ERISA. Furthermore, he disagreed with the majority's view that a law "relates to" an employee benefit plan if it has a connection with or reference to such a plan; instead, he proposed that only laws specifically designed to affect such plans should be considered as relating to them. Thus, according to him, D.C.'s Worker's Compensation Equity Amendment Act did not relate directly enough to warrant preemption under ERISA.