The Social Security Act provides spousal benefits for wives, husbands, widows, and widowers of retired and disabled wage earners. Prior to December 1977, benefits were payable only to those husbands or widowers who could demonstrate their dependency on their wage-earning wives for one-half of their support. Wives and widows were entitled to spousal benefits without any showing of dependency on their husbands. Under Califano v. Goldfarb, that regulation was held to violate equal protection. Congress then repealed the dependency requirement for widowers and husbands. To offset the increased costs, Congress included a pension-offset provision but exempted from the pension offset those spouses who were eligible to receive pension benefits prior to December 1982 and who would have qualified for unreduced spousal benefits under the Act as it was in effect and being administered in 1977. A severability clause was also included in the amended act. Mathews (P) retired from his job with the U.S. Post Office in 1977. His wife who had retired a few months earlier was fully insured under Social Security. Mathews applied for husband's benefits on his wife's account. Mathews was informed he was entitled to benefits but that the entire amount would be offset by his retirement of $573 per month from the Post Office. An ALJ judge affirmed that decision. The Appeals Council affirmed. Mathews then brought this class action against the Secretary; the offset for men but not for woman violated due process and the severability clause of the 1977 Amendment was unconstitutional. The class was certified. The court determined that the offset exception and the severability clause were unconstitutional. The Supreme Court granted review.