In Exxon Corp. et al. v. Governor of Maryland et al., the Supreme Court ruled in favor of a Maryland law that prohibited oil producers and refiners from operating retail service stations within the state, even though it effectively barred major out-of-state companies like Exxon from doing so. The court held that this did not violate the Commerce Clause as it applied equally to all producers and refiners regardless of their location or interstate commerce involvement, nor did it discriminate against interstate goods or favor local ones unfairly. Furthermore, they found no violation of Equal Protection Clause as there was a rational basis for the legislation - namely preventing predatory pricing practices and promoting competition among independent dealerships.

In the dissenting opinion for Exxon Corp. v. Governor of Maryland, Justice Rehnquist argued that the majority's decision was inconsistent with previous rulings on interstate commerce and economic protectionism. He contended that the court had previously struck down state laws which favored local over out-of-state businesses, even when those laws did not explicitly discriminate against interstate commerce. In this case, he believed that Maryland's law banning oil producers from operating retail gas stations within its borders disproportionately impacted out-of-state companies like Exxon while benefiting in-state independent dealerships - a form of economic protectionism contrary to Commerce Clause jurisprudence. Furthermore, he disputed the majority’s assertion that there were no constitutional issues because all corporations were treated equally under Maryland law; instead asserting it was clear certain entities would be more affected than others due to their business models or geographical locations.