Writing for the Court, Justice William Brennan first established that under a traditional equal protection analysis, a legislative classification must be sustained if it’s rationally related to a legitimate government interest. Brennan explained that since the statutory classification of households “is clearly irrelevant to the stated purposes of the Act,” it must rationally further a government interest other than those listed in the congressional “declaration of policy.” Brennan lamented the lack of legislative history for the amendment but found evidence indicating that it was proposed to prevent “hippies” and “hippie communes” from participating in the food stamp program. Brennan found that the classification “clearly” couldn’t be supported by referencing that purpose because “if the constitutional conception of ‘equal protection of the laws’ means anything, it must at the very least mean that a bare congressional desire to harm a politically unpopular group cannot constitute a legitimate governmental interest.”

The government argued that the purpose of the amendment was to prevent fraud and that Congress might have rationally thought (1) that households with one or more unrelated members are more likely than “fully related” households to contain individuals who abuse the program by fraudulently failing to report sources of income or by voluntarily remaining poor; and (2) such households are “relatively unstable,” which increased the difficulty of detecting abuses. In response, Brennan described the government’s argument as “wholly unsubstantiated assumptions” and stated that even if the Court agreed, it couldn’t conclude that denial of essential federal assistance to all otherwise eligible households with unrelated members is a rational effort to address fraud.

Brennan noted that the Food Stamp Act already addressed the issue of fraud independent of Congress’ 1971 amendment. He wrote that “[t]he existence of these provisions necessarily casts considerable doubt upon the proposition that the 1971 amendment could rationally have been intended to prevent those very same abuses.” Brennan argued that the practical effect of the amendment is not to prevent fraud, but rather to exclude from the program “not those persons who are ‘likely to abuse the program,’ but, rather, only those persons who are so desperately in need of aid that they cannot even afford to alter their living arrangements so as to retain their eligibility.” Ultimately, Brennan concluded that the distinction created by the amendment was unconstitutional, writing that “[t]raditional equal protection analysis does not require that every classification be drawn with precise ‘mathematical nicety.’ But the classification here in issue is not only ‘imprecise,’ it is wholly without any rational basis.”