APPEAL FROM THE UNITED STATES DISTRICT COURT FOR THE NORTHERN DISTRICT OF ILLINOIS.
Brennan, J., delivered the opinion of the Court, in which Douglas, Stewart, White, Marshall, and Blackmun, JJ., joined. Burger, C. J., filed an opinion concurring in the result, post, p. 292.
MR. JUSTICE BRENNAN delivered the opinion of the Court.
Appellants, two college students and their mothers, brought this class action in the District Court for the Northern District of Illinois alleging that § 4-1.1 of the Illinois Public Aid Code, Ill. Rev. Stat., c. 23, § 4-1.1 (1967) and the implementing Illinois Public Aid Regulation 150 violate the Equal Protection Clause of the Fourteenth Amendment, and, because inconsistent with § 406 (a)(2)(B) of the Social Security Act, 42 U. S. C. § 606 (a)(2)(B), also violate the Supremacy Clause of the Constitution.*fn1 Under the Illinois statute and regulation
needy dependent children 18 through 20 years of age who attend high school or vocational training school are eligible for benefits under the federally assisted Aid to Families With Dependent Children (AFDC) program, 42 U. S. C. § 601 et seq., but such children who attend a college or university are not eligible.*fn2 Section 406 (a)(2) of
the Social Security Act, on the other hand, defines "dependent child" to include a child ". . . (B) under the age of twenty-one and (as determined by the State in accordance with standards prescribed by the Secretary) a student regularly attending a school, college, or university, or regularly attending a course of vocational or technical training designed to fit him for gainful employment." A three-judge district court held that neither constitutional contention had merit and sustained the validity of the Illinois statute and regulation. 314 F.Supp. 1082 (1970). We noted probable jurisdiction, 401 U.S. 906 (1971). We hold that the Illinois statute and regulation conflict with § 406 (a)(2)(B) and for that reason are invalid under the Supremacy Clause. We therefore reverse on that ground without reaching the equal protection issue.
Section 402 (a)(10) of the Social Security Act provides that state participatory plans submitted under the AFDC program for the approval of the Secretary of the Department of Health, Education, and Welfare (HEW) must provide "that aid to families with dependent children shall be furnished with reasonable promptness to all eligible individuals." (Emphasis supplied.) In King v. Smith, 392 U.S. 309 (1968), we considered whether a State participating in an AFDC program may, consistently with the Supremacy Clause, adopt eligibility standards that exclude from benefits needy dependent children eligible for benefits under applicable federal statutory standards. There was before us in that case a regulation of the Alabama Department of Pensions and Security that treated a man who cohabited with the mother of needy dependent children in or outside the home as a nonabsent "parent" within the federal statute. Since aid can be granted under § 406 (a) of the Federal
Act only if a "parent" of the needy child is continually absent from the home, Alabama's regulation resulted in the ineligibility of the children for benefits. We held that the Alabama regulation defined "parent" in a manner inconsistent with § 406 (a) of the Social Security Act and therefore that in "denying AFDC assistance to [children] on the basis of this invalid regulation, Alabama has breached its federally imposed obligation to furnish 'aid to families with dependent children . . . with reasonable promptness to all eligible individuals . . . .'" 392 U.S., at 333.
Thus, King v. Smith establishes that, at least in the absence of congressional authorization for the exclusion clearly evidenced from the Social Security Act or its legislative history, a state eligibility standard that excludes persons eligible for assistance under federal AFDC standards violates the Social Security Act and is therefore invalid under the Supremacy Clause. We recognize that HEW regulations seem to imply that States may to some extent vary eligibility requirements from federal standards.*fn3 However, the principle that accords substantial weight to interpretation of a statute by the department entrusted with its administration is inapplicable insofar as those ...