In the case of Lyng, Secretary of Agriculture v. Castillo et al., 1985, the U.S. Supreme Court ruled on a dispute regarding food stamp eligibility for households with unrelated individuals living together. The appellants were members of such households who had been denied food stamps under a provision in the Food Stamp Act that defined "household" as an individual or group of related individuals living together as one economic unit but excluded groups of unrelated individuals from this definition. They argued that this provision violated their Fifth Amendment right to equal protection by discriminating against them based on familial status. The court upheld the constitutionality of the provision and rejected these claims, ruling 6-3 in favor of Richard E.Lyng, then-Secretary Of Agriculture. It held that Congress was within its rights to differentiate between different types and structures of households when determining eligibility for public assistance programs like food stamps because it could reasonably conclude that related persons are more likely than unrelated ones to pool resources and share expenses.

In the dissenting opinion for Lyng, Secretary of Agriculture v. Castillo et al., Justice Thurgood Marshall argued that the majority's decision was inconsistent with previous rulings and violated principles of equal protection under law. He contended that there was no rational basis to distinguish between households where members are related by blood or marriage and those where they are not in terms of food stamp allocation. The distinction made by Congress, he believed, did not serve any legitimate governmental interest but rather perpetuated harmful stereotypes about non-traditional families. Furthermore, he pointed out that this ruling could potentially harm innocent children living in these households who rely on food stamps for their nutritional needs. In his view, the Court should have struck down this discriminatory provision as unconstitutional.