In the case of Califano v. Westcott, 1978, the US Supreme Court ruled that a provision in the Social Security Act was unconstitutional because it discriminated on the basis of gender. The contested provision provided benefits to families with dependent children who had been deprived of parental support due to the unemployment of their father but did not provide for families where mothers were unemployed. This violated equal protection principles under Fifth Amendment's Due Process Clause as interpreted by previous court decisions which prohibit federal government from engaging in sex-based discrimination unless it serves an important governmental objective and is substantially related to achieving that objective. In this case, no such substantial relationship existed between gender-based distinction and any important governmental objectives (like administrative convenience or reflecting traditional views about family roles). Therefore, rather than invalidating entire program or denying relief to plaintiffs (who sought extension rather than termination), court ordered Secretary of Health, Education & Welfare (HEW) - Joseph A Califano Jr., at time - to extend benefits until Congress could amend law.

In the dissenting opinion for Califano v. Westcott, Justice Rehnquist disagreed with the majority's view that Section 407 of the Social Security Act was unconstitutional due to gender discrimination. He argued that this provision, which only provided benefits to families where a father was unemployed but not when a mother was unemployed, did not violate equal protection principles because it reflected Congress' reasonable attempt to address societal issues based on statistical realities at that time - namely, men were more likely than women to be primary wage earners in families and their unemployment would therefore have greater financial impact on family welfare. Furthermore, he contended that courts should defer to legislative judgment unless there is clear evidence of irrationality or arbitrariness in such classifications made by Congress.