The "rational basis" standard of review emerged in the late 1930s, as the Supreme Court retreated from its earlier activism in the defense of economic liberties. We owe the phrase to Justice harlan fiske stone, who used it in two 1938 opinions to signal a new judicial deference to legislative judgments. In united states v. carolene products co. (1938), Stone said that an economic regulation, challenged as a violation of substantive due process or of equal protection, would be upheld unless demonstrated facts should "preclude the assumption that it rests upon some rational basis within the knowledge and experience of the legislators." In South Carolina State Highway Department v. Barnwell Brothers, Inc. (1938), Stone proposed "rational basis" as the standard for reviewing state regulations of commerce. (Later, Stone would accept the necessity for more exacting judicial scrutiny of such laws.) To complete the process, the Court adopted the same deferential posture toward congressional judgments that local activities substantially affected interstate commerce and thus might be regulated by Congress under the commerce power. In all its uses, "rational basis" represents a strong presumption of the constitutionality of legislation.
Yet even so minimal a standard of judicial review does, in theory, call for some judicial scrutiny of the rationality of the relationship between legislative means and ends. And that scrutiny of means makes sense only if we assume that the ends themselves are constitutionally required to serve general, public aims; otherwise, every law would be self-justifying, as precisely apt for achieving the advantages and disadvantages it achieves. Although the Court has sometimes suggested in economic regulation cases that even a search for legislative rationality lies beyond the scope of the judicial function, some such judicial scrutiny is required if our courts are to give effect to generalized constitutional guarantees of liberty and equality. Today's assumption, therefore, is that a law depriving a person of liberty or of equal treatment is invalid unless, at a minimum, it is a rational means for achieving a legitimate legislative purpose.
Even so relaxed a standard of review appears to call for a judicial inquiry always beset by uncertainties and often dominated by fictitious assumptions. Hans Linde has demonstrated the unreality attendant on judicial efforts to identify the "purposes" served by a law adopted by legislators with diverse objectives, or objectives only tenuously connected to the public good. Lacking sure guidance as to those "purposes"—which may have changed in the years since the law was adopted—a court must rely on counsel's assertions and its own assumptions. But in its inception the rational basis standard was not so much a mode of inquiry as a formula for validating legislation. Thus, in mcgowan v. maryland (1961), the Supreme Court said, "A statutory discrimination will not be set aside if any state of facts reasonably may be conceived to justify it." Part of the reason why the rational basis standard survives in federal constitutional law is that it is normally taken seriously only in its permissive feature (United States Railroad Retirement Board v. Fritz, 1980). A number of state courts, interpreting state constitutional law, do take the rational basis standard to require a serious judicial examination of the reasonableness of legislation. And the Supreme Court itself, in its late-1960s forays into the reaches of equal protection doctrine lying beyond racial equality, sometimes labeled legislative classifications as "irrational" even as it insisted that state-imposed inequalities be justified against more exacting standards of review. (See harper v. virginia state board of elections; levy v. louisiana; shapiro v. thompson.) Since that time, the explicit recognition of different levels of judicial scrutiny of legislation has allowed the Court to reserve the rhetoric of rational basis for occasions thought appropriate for judicial modesty, in particular its review of "economic and social regulation." Some substantive interests call for heightened judicial scrutiny of legislative incursions into them; absent such considerations, the starting point for constitutional analysis remains the rational basis standard.
Kenneth L. Karst
Linde, Hans A. 1976 Due Process of Lawmaking. Nebraska Law Review 55:197–255.