We found that justices vary widely in their inclination to strike down Congressional laws. Justice Clarence Thomas, appointed by President George H. W. Bush, was the most inclined, voting to invalidate 65.63 percent of those laws; Justice Stephen Breyer, appointed by President Bill Clinton, was the least, voting to invalidate 28.13 percent. The tally for all the justices appears below.
  One conclusion our data suggests is that those justices often considered more "liberal" - Justices Breyer, Ruth Bader Ginsburg, David Souter and John Paul Stevens - vote least frequently to overturn Congressional statutes, while those often labeled "conservative" vote more frequently to do so. At least by this measure (others are possible, of course), the latter group is the most activist.

  While I agree that the conservative justices have not consistently embraced judicial restraint, this argument nonetheless strikes me as weak. First, using judicial invalidation as a proxy for activism suffers from an obvious flaw: If a legislature passes a plainly unconstitutional law, striking down the statute by applying established precedents reflects neither separation-of-powers activism nor precedent activism. (Cass Sunstein cures this problem by actually defining judicial activism as the act of invalidation, but, as noted earlier, I don't find this definition otherwise helpful.)
  Consider the Dickerson case that upheld Miranda. The Supreme Court's decision not to overrule Miranda required it to strike down a 1968 federal law Congress had passed to thumb its nose at the Warren Court. It's hard to see Dickerson as an activist decision: The court adhered to precedent and confirmed that a law long thought to be unconstitutional was in fact invalid. However, critics include Dickerson in the list of cases that are supposed to prove the court's conservative activism.
  Similarly, the focus on decisions striking down federal laws unfairly stacks the deck against the Rehnquist Court. The Warren Court's reform efforts focused primarily on invalidating state and local laws, rather than federal laws. Indeed, the Warren Court generally tried to expand the scope of federal laws such as Section 1983 and other federal civil rights laws. As a result, using judicial invalidation of federal laws as a quantitative measure of activism seems particularly unhelpful. Perhaps the more relevant quantitative measure would compare how often the Rehnquist Court and Warren Court have struck down legislative acts as a whole, or, better yet, how often they have overruled precedents. I suspect it would reveal a very different picture.
  It's also a mistake to assume that every Rehnquist Court decision striking down a legislative act features the conservative justices acting over the dissents of more liberal colleagues. Based on my review of the last Supreme Court term [October Term 2002 — Ed.], it's more often the other way around. I recently examined last year's Supreme Court cases looking for decisions in which the more conservative and more liberal justices disagreed about the constitutionality of existing laws or administrative acts. In cases that split the justices into relatively predictable ideological camps, I asked, which group voted to invalidate the other branches more often? The more conservative justices (William Rehnquist, Antonin Scalia, Clarence Thomas, and sometimes Anthony Kennedy and Sandra Day O'Connor) or the more liberal ones (David Souter, Stephen Breyer, John Paul Stevens, and Ruth Bader Ginsburg)?
  Roughly a dozen of the court's 83 cases involved fairly clear ideological splits on the scope of constitutional rights. (Many cases did not involve constitutional questions at all, and those that did usually failed to produce neat camps of left versus right.) Within the dozen or so cases, however, the more liberal justices favored striking down the other branch of government almost twice as often as the conservatives did.