Nearly a year ago, I had an engaging debate at Berkeley Law School regarding "judicial activism." Of course, as I clarified, the phrase is really just an epithet hurled by someone to describe a legal ruling with which he disagrees. The whole argument about whether a certain judge is "activist," "restrained," or anything else is irrelevant: fidelity to the Constitution should be the sole evaluative criterion---and point of debate---regardless of whether that means striking down a law or upholding it, deferring to the legislature or not.
As I said during this debate (which was against a young law professor named Fred Smith),
The purveyors of conventional punditry all miss the larger point. The role of the judiciary in terms of constitutional interpretation is to fully interpret and apply the Constitution, period. So, if that means upholding a law, fine. If that means striking it down, fine. Activism is doing something that is not supposed to be the judicial role or not being faithful to the Constitution, which is no small task in part because of the doctrinal mess the Supreme Court has made. Again, whether a particular statute stands or falls is of no moment. Fidelity to the founding document should be the touchstone, not a circular debate over the virtues of judicial restraint or---as John Roberts put it at his confirmation hearing---modesty: just calling balls and strikes, just being in a kind of modest judicial role. Again, where you stand on those sorts of debates depends on where you sit.
I can quote this debate because a transcript has been published in the Federalist Society's journal, Engage. The current volume has plenty of other interesting articles, including some authored by various Cato-affiliated or -friendly folks.