Writing for the Court, Justice William Brennan emphasized that gender-based classifications must meet a standard of heightened scrutiny. While the counsel for Oklahoma argued that the law aimed to enhance traffic safety by addressing statistical evidence suggesting that young males were more prone to driving under the influence of alcohol than females, Brennan found this evidence to be unpersuasive and insufficient to justify the gender-based distinction. He pointed out that the disparity in arrest rates for alcohol-related offenses between males and females in the 18-20 age group—while existent—was not substantial enough to warrant a categorical distinction based on sex. He noted that only 2% of males and 0.18% of females in the relevant age group had been arrested for driving under the influence, which he argued was an overly broad generalization and an inadequate basis for such a law. Brennan stated that “proving broad sociological propositions by statistics is a dubious business” and emphasized that the Equal Protection Clause does not allow for classifications based on loose-fitting generalities about gender behavior.

Brennan rejected Oklahoma’s argument that the statute could be justified under the Twenty-first Amendment, which grants states broad powers to regulate alcohol. He asserted that the Amendment does not permit states to impose invidious discrimination in violation of the Equal Protection Clause. In this case, Brennan found that the gender-based restriction on beer sales was not sufficiently connected to the state’s interest in traffic safety to survive constitutional scrutiny. Ultimately, Justice Brennan concluded that Oklahoma’s gender-based beer sales law was an invidious discrimination against males aged 18-20, in violation of the Equal Protection Clause. He found the law lacked the necessary substantial relation to the state’s goal of promoting traffic safety, reversing the lower court’s decision.