During his early years on the Court, despite the presence of three other Republican appointees, Rehnquist was often the only dissenter, espousing a view of states' rights and limited federal judicial power that many regarded as outmoded. He resisted the view of the other eight members of the Court that the Equal Protection Clause of the Fourteenth Amendment applied to, and required heightened scrutiny of, state-sponsored discrimination against illegitimate children, resident aliens, and women. Indeed, he insisted that the Equal Protection Clause had only marginal application beyond cases of racial discrimination. In the area of criminal procedure, Rehnquist urged the Court to overturn Mapp v. Ohio (1961), which made the rule excluding illegally seized evidence from admission in a trial applicable to the states. Rehnquist also seemed hostile to Miranda v. Arizona (1966), which guaranteed that suspects in police custody be informed of their rights before interrogation, although he never directly argued that it should be reversed.

Still, even in his early years on the Court, Rehnquist was less likely to be in dissent than liberal justices William O. Douglas, William J. Brennan, Jr., and Thurgood Marshall. The ideas expressed in some of Rehnquist's early dissents became influential in later majority opinions. As Harvard law professor Laurence Tribe observed, "Even in lone dissent, he has helped define a new range of what is possible."

When dissenting, Rehnquist made his most telling points in opposition to the majority's efforts to enact "desirable" social policy with little support from the constitutional or statutory provisions they are supposed to be interpreting. An example is United Steel Workers of America v. Weber (1979). This case involved an affirmative action plan devised by the Kaiser Aluminum and Chemical Company and the United Steel workers. The "voluntary" plan reserved for blacks half of available positions in an on-the-job training program. Brian Weber, excluded solely because he was white, filed suit based on Title VII of the Civil Rights Act of 1964, which provides that "it shall be unlawful for an employer … to fail or refuse to hire … any individual . . . because of such individual's race." The statute goes on to say that its provisions are not to be interpreted "to require any employer … to grant preferential treatment to any individual or group." Nevertheless, a 5-2 majority reversed the lower courts, finding that the discrimination against whites was not against the "spirit" of Title VII and consequently not prohibited. In a bitter dissent, Rehnquist concluded that "close examination of what the Court proffers as the spirit of the Act reveals it as the spirit of the present majority, not the 88th Congress."

Rehnquist also dissented in Roe v. Wade (1973), in which the majority based a woman's right to an abortion on a constitutional right of privacy that arose not from the terms but from the "penumbras" of the Bill of Rights. He wrote, "To reach its result, the Court necessarily has had to find within the scope of the Fourteenth Amendment a right that was apparently completely unknown to the drafters of the Amendment."

The 1975 term saw Rehnquist come into his own as the leader of the ever-shifting conservative wing of the Court. He wrote several majority opinions that cut back the power of the federal government vis-à-vis the states. The most notable of these was National League of Cities v. Usery, in which Rehnquist used an expansive reading of the Tenth Amendment to strike down a federal statute that regulated the wages and hours of state government employees, although such regulation was within Congress's commerce power. The opinion showed that if faced with a choice between judicial restraint and states' rights, doctrines he generally supported, Rehnquist was prepared to defend states' rights more aggressively.

When Warren Burger announced his resignation as chief justice and President Ronald Reagan nominated Rehnquist as his replacement June 20, 1986, there was a firestorm of protest among liberals. Sen. Edward Kennedy denounced Rehnquist as having an "appalling record on race," and liberal columnists branded him a right-wing extremist. A concerted effort was undertaken to find something in his past that might provide a basis for defeating the nomination. Assorted allegations were raised concerning harassment of black voters when he was a Republican party official in Phoenix, the handling of a family trust, a memo he had written to Justice Jackson as a law clerk urging that the "separate but equal" doctrine not be overruled in Brown v. Board of Education (1954), and racially restrictive covenants in the deeds to his Phoenix house and summer home in Vermont. The Senate perceived that these allegations were either unproven or, if true, were "ancient history" and irrelevant to his fitness for the post of chief justice. Significantly, no serious charge of misconduct was alleged as to Rehnquist's nearly fifteen years as an associate justice. After much controversy, he was confirmed September 17 by a 65-33 vote.

If the 1975 term saw Rehnquist become a major force on the Court, it was the 1987 term, his second year as chief justice, that saw him mature in that position. In a speech he gave in 1976 Rehnquist had discussed the role of the chief justice, citing Charles Evans Hughes as his model because of his strong belief in unanimity of decision and his willingness to modify his opinions in order to attract additional votes.

Following that advice, in the 1987 term he achieved a high level of agreement with his fellow justices, ranging from 57.6 percent with Thurgood Marshall to 83.1 percent with Anthony Kennedy. His managerial abilities in the 1987 term won the praise of Justice Harry Blackmun, who deemed him a "splendid administrator in conference." For the first time in years, the Court concluded its work prior to July 1, in part because it had taken on fewer cases.

During the 1987 term, Rehnquist also showed that he could be flexible, joining with the more liberal justices to subject the dismissal of a homosexual CIA agent to judicial review and to support the freedom of speech claims of Hustler magazine to direct off-color ridicule at a public figure. Most significant, in Morrison v. Olson (1988) Rehnquist wrote the majority opinion upholding Congress's right to appoint independent counsels to investigate and prosecute high government officials, a right that was challenged by the Reagan administration.

Rehnquist was an effective manager whose humor and fairness contributed to the cordial relations among the justices. He enjoyed a variety of hobbies, including oil painting, singing, stamp collecting, theater-going, and poker. Rehnquist, a widower since 1991, found time to write three popular books on the Court's history: The Supreme Court: How It Was, How It Is (1988), Grand Inquests: The Historic Impeachments of Justice Samuel Chase and President Andrew Johnson (1992), and Centennial Crisis: The Disputed Election of 1876 (2004). He was diagnosed with thyroid cancer in October 2004 and died on September 3, 2005 at age 80.

William H Rehnquist