For example, Michael W. McConnell has written that Congress never "required that the schools of the District of Columbia be segregated." According to that rationale, the segregation of schools in Washington D.C. was unauthorized and therefore illegal. Despite the undoubted importance of "Brown", much of modern equal protection jurisprudence originated in other cases, though not everyone agrees about "which" other cases. Many scholars assert that the opinion of Justice Harlan Stone in "United States v. Carolene Products Co." (1938) contained a footnote that was a critical turning point for equal protection jurisprudence, but that assertion is disputed. Whatever its precise origins, the basic idea of the modern approach is that more judicial scrutiny is triggered by purported discrimination that involves "fundamental rights" (such as the right to procreation), and similarly more judicial scrutiny is also triggered if the purported victim of discrimination has been targeted because he or she belongs to a "suspect classification" (such as a single racial group). This modern doctrine was pioneered in "Skinner v. Oklahoma" (1942), which involved depriving certain criminals of the fundamental right to procreate:  When the law lays an unequal hand on those who have committed intrinsically the same quality of offense and sterilizes one and not the other, it has made as invidious a discrimination as if it had selected a particular race or nationality for oppressive treatment. Until 1976, the Supreme Court usually ended up dealing with discrimination by using one of two possible levels of scrutiny: what has come to be called "strict scrutiny" (when a suspect class or fundamental right is involved), or instead the more lenient "rational basis review". Strict scrutiny means that a challenged statute must be "narrowly tailored" to serve a "compelling" government interest, and must not have a "less restrictive" alternative. In contrast, rational basis scrutiny merely requires that a challenged statute be "reasonably related" to a "legitimate" government interest. However, in the 1976 case of "Craig v. Boren", the Court added another tier of scrutiny, called "intermediate scrutiny", regarding gender discrimination. The Court may have added other tiers too, such as "enhanced rational basis" scrutiny, and "exceedingly persuasive basis" scrutiny. All of this is known as "tiered" scrutiny, and it has had many critics, including Justice Thurgood Marshall who argued for a "spectrum of standards in reviewing discrimination", instead of discrete tiers. Justice John Paul Stevens argued for only one level of scrutiny, given that "there is only one Equal Protection Clause".