The U.S. Supreme Court case Pharmaceutical Research and Manufacturers of America v. Peter E. Walsh, Acting Commissioner, Maine Department of Human Services et al., 2002 revolved around a dispute over the legality of a state program aimed at controlling prescription drug costs for uninsured residents in Maine. The Pharmaceutical Research and Manufacturers of America (PhRMA) argued that this program violated Medicaid law by imposing conditions on manufacturers beyond those specified in the federal statute governing rebates to states under Medicaid's prescription drug benefit provision. They also claimed it infringed upon Congress' power to regulate interstate commerce by effectively regulating prices outside Maine’s borders. However, the Supreme Court ruled against PhRMA stating that there was no preemption by federal law as long as states were not directly setting prices but rather using their bargaining power to negotiate lower rates with pharmaceutical companies for their citizens who otherwise could not afford them.

In the dissenting opinion for the case of Pharmaceutical Research and Manufacturers of America v. Walsh, Justice Scalia argued that Maine's prescription drug program violated federal law. He contended that the state was essentially imposing a tax on pharmaceutical manufacturers to fund its Medicaid program, which is not allowed under federal Medicaid laws. Furthermore, he disagreed with the majority's interpretation of "nominal" copayments in relation to this case and believed it should be interpreted as meaning small or insignificant rather than just any amount set by states. He also expressed concerns about potential negative impacts on interstate commerce due to differential treatment between in-state and out-of-state pharmacies under Maine’s plan.