In the case of Gulf Oil Corp. et al. v. Copp Paving Co., Inc., et al., 1974, the Supreme Court ruled in favor of Gulf Oil Corporation and other oil companies against Copp Paving Company and others who alleged that they had been charged excessive prices for asphalt due to a conspiracy among oil companies to fix prices, violating antitrust laws. The court held that federal courts should not apply state law retroactively when it interferes with federal interests or policies such as those under the Sherman Act (antitrust legislation). In this case, California's attempt to apply its own antitrust laws was deemed inappropriate because it conflicted with existing federal policy on interstate commerce and competition.

In the dissenting opinion for Gulf Oil Corp. v. Copp Paving Co., Inc., Justice Brennan, joined by Justices Douglas and Marshall, argued that the majority's decision to uphold a state law restricting interstate commerce was inconsistent with previous Supreme Court rulings on similar issues. They contended that California's requirement for asphalt manufacturers to have an in-state processing plant effectively discriminated against out-of-state companies and placed an undue burden on interstate commerce. The dissenters also disagreed with the majority's assertion that this case was different from others because it involved natural resources; they believed this distinction did not justify upholding a discriminatory law. Furthermore, they criticized the majority for failing to consider whether there were less restrictive alternatives available to achieve California’s goal of conserving its natural resources.