In the case of Shell Oil Co. v. Dartt, 1977, the U.S Supreme Court ruled in favor of Shell Oil Company against a claim made by Dartt that they had violated antitrust laws. The dispute arose when Dartt alleged that Shell was engaging in price discrimination through its "Dealer Tank Wagon" (DTW) pricing policy which allowed it to sell gasoline at different prices depending on location and competition levels. This practice allegedly disadvantaged independent gas station operators like Dartt who were unable to compete with lower-priced corporate-owned stations nearby due to this differential pricing strategy from suppliers such as Shell. The court held that for an antitrust violation under the Robinson-Patman Act's prohibition on price discrimination to occur, there must be a reasonable possibility of harm to competition resulting from discriminatory pricing practices over time rather than just individual instances or isolated occurrences of potential competitive disadvantage caused by these practices. Therefore, since no substantial evidence was presented showing any long-term detrimental effect on market competition because of DTW policy implementation by oil companies including Shell, the Supreme Court concluded that there was no violation committed under federal antitrust law provisions.

The dissenting opinion in the Shell Oil Co. v. Dartt case argued that the majority's decision to allow private individuals to bring lawsuits under the Robinson-Patman Act was a misinterpretation of Congressional intent and an overreach of judicial authority. The dissenters believed that Congress intended for enforcement actions under this act to be brought by governmental entities, not private parties, as evidenced by its placement within a larger statutory scheme primarily enforced by public officials. They also pointed out that allowing such suits could lead to excessive litigation and potentially unjust results due to varying interpretations of complex pricing practices across different courts. Furthermore, they expressed concern about potential negative impacts on competition if businesses had to constantly defend against these types of claims.