Atrios posted a piece titled "Judicial Activism" (over at Eschaton) that overturns the applecart of conventional wisdom on the subject. He references a NYT article from July, "So Who Are the Activists?" that begins:
When Democrats [less often] or Republicans [quite frequently] seek to criticize judges or judicial nominees, they often resort to the same language. They say that the judge is "activist." But the word "activist" is rarely defined. Often it simply means that the judge makes decisions with which the critic disagrees.
The authors started with the presumption that "a marked pattern of invalidating Congressional laws certainly seems like one reasonable definition of judicial activism," and examined the current Supreme Court, (its members have been unchanged since 1994). Here is their conclusion:
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.
Thomas 65.63 %
Kennedy 64.06 %
Scalia 56.25 %
Rehnquist 46.88 %
O'Connor 46.77 %
Souter 42.19 %
Stevens 39.34 %
Ginsburg 39.06 %
Breyer 28.13 %
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.
Artios concludes, "Judicial Activism usually means nothing more than 'Judgifying I don't like.' In other words, it means nothing."