In the 1986 case of California Federal Savings & Loan Association v. Guerra, the U.S. Supreme Court ruled in favor of a California law requiring employers to provide up to four months unpaid disability leave for pregnant employees, as well as reinstatement after this period. The court held that this law did not violate Title VII of the Civil Rights Act which prohibits sex discrimination in employment because it was not an instance of preferential treatment but rather a measure designed to ensure equal opportunity for women affected by pregnancy-related disabilities. This decision affirmed that states could enact laws providing greater protections than those offered under federal anti-discrimination statutes without violating these statutes.

In the dissenting opinion for California Federal Savings & Loan Assn. v. Guerra, Justice Thurgood Marshall argued that the majority's decision was a misinterpretation of Title VII of the Civil Rights Act and its intent to prevent sex discrimination in employment practices. He believed that by upholding California’s Pregnancy Disability Leave (PDL) statute, which mandated employers to provide leave and job reinstatement to employees disabled by pregnancy but not those with other disabilities, it allowed for preferential treatment based on sex rather than ensuring equal opportunity as intended by federal law. Furthermore, he contended this ruling undermined Congress' goal of treating pregnancy-related conditions like any other medical condition under non-discrimination laws. In his view, while states should be able to enact legislation providing greater protection against discrimination than federal law does; they shouldn't be permitted to create benefits exclusive only for one gender group without violating Title VII's prohibition against sex-based classifications.