"As a matter of fact, in just two years, these same nominees have either disregarded or overturned precedent in at least eight other cases; a case involving assignments to attain racial diversity in school assignments, a case overruling 70 years of precedent on the Second Amendment and federal gun control law, a case which increased the burden of proof on older workers to prove age discrimination, a case overturning a 1911 decision to allow manufacturers to set minimum prices for their products, a case overruling two cases from the 1960s on time limits for filing criminal appeals, a case reversing precedent on the Sixth Amendment right to counsel, a case overturning a prior ruling on regulation of issue ads relating to political campaigns, and a case regarding prior law and creating a new standard that limits when cities can replace civil service exams that they may believe have been -- have discriminated against a group of workers.
So I do not believe that Supreme Court justices are merely umpires calling balls and strikes. Rather, I believe that they make the decisions of individuals who bring to the Court their own experiences and philosophies." Senator Dianne Feinstein
During his confirmation hearings, Justice (then Court of Appeals Judge) John Roberts likened his role on the Supreme Court to that of an umpire who calls "balls" and "strikes." He, I believe, minimized the role which he (and any justice for that matter) has in deciding who wins and who loses cases.
Umpires however don't change the rules. They apply them. Supreme Court justices can decide for themselves which rules (or precedents) they will uphold and which ones they will break (or overturn). The Supreme Court that once deemed "separate but equal" permissible later held it unconstitutional and the Supreme Court that once upheld laws banning dissent in times of war later upheld the right of schoolchildren no less the right to wear arm bands protesting our war policies.
One need only look at two cases where Justices Antonin Scalia and Clarence Thomas, two conservative "umpires" voted differently. Justice Antonin Scalia voted to overturn a law banning flag burning; Chief Justice William Rehnquist voted to uphold it. Justice Scalia voted to release a U.S. citizen whom Bush held as an enemy war combatant while Justice Thomas voted to uphold the citizen's incarceration. Both cases dealt with enumerated (explicitly cited) rights guaranteed by our Constitution.
The first concerned the First Amendment's free speech clause while the second concerned habeas corpus rights (which as the Constitution explicitly makes clear, cannot be suspended without an act of Congress). How can these two conservative justices differ in how the law is interpreted? Scalia thinks the First Amendment implicitly protects the right to free expression even though it explicitly only protects the right to free speech. Rehnquist evidently did not.
Scalia treated Hamdi v Rumsfeld as a criminal case while Thomas considered the defendant's incarceration as an act in war.