Sandy Levinson makes the argument in favor of judicial term limits. Before I get to some potential objections, I think a couple points should be emphasized. First, it's abundantly clear that life tenure is in no way a requirement of liberal democracy -- as Levinson notes, the United States is an extreme outlier among constitutional democracies, and non-renewable terms with good pensions are clearly sufficient to protect judicial independence. Second, there are some very clear costs associated with life tenure. The most important are 1)the possibility that judges will stay on although they clearly no longer have the capacity to serve (which is not hypothetical; cf. Rehnquist and Douglas) and 2)the fact that what presidents get appointments is a random process that leads to a skewed composition of the courts (again, not hypothetical; Nixon got twice as many appointments in six years as Carter and Clinton got in twelve, with real political consequences.) The fact that younger judges can serve longer compounds this arbitrariness.
So what advantages could life tenure have that could outweigh the undeniable costs? One potential response is nightmare scenarios. With all do respect, this response has to be considered highly unconvincing. It should first of all be noted that the alleged bad consequences involved in a president appointing five justices depends entirely on an unlikely 15-year limit rather than the much more likely 18-year limit (one every two years.) And, of course, a two-term president could easily get 4 or 5 appointments under the current system anyway. But more importantly, it simply misunderstands the nature of judicial power, which is by its nature politically marginal and dependent on the other branches.
First of all, if the other branches of government started to agree with Thomas that the New Deal was unconstitutional, it wouldn't matter what the Supreme Court thought because they could just repeal the programs. Nor would I be worried about the return of the "Constitution-in-Exile," because if the Court tried to impose pre-1936 constitutional rules in the current polity it would stick for about 10 minutes. The judiciary will never win that kind of power struggle with the political branches, and this is just as true when they have life tenure as when they have long term limits. (And, of course, if the courts were violently out of step with the political branches the government could easily make life tenure irrelevant by just adding more justices to the Court.) I also think it exaggerates things greatly to say that Bush v. Gore proved that the courts are all-powerful, since after all the only political actors who could have challenged the Court agreed with the Court. If the Court had also decided McCain v. Obama, that would be different, but of course they wouldn't. I don't think that such hypothetical are very useful. (And, of course, it ignores the other side of the coin: situations like the New Deal when reactionary holdovers of the old regime obstruct political change strongly favored by the elected branches.)
Another argument about judicial independence is that judges who have to retire will be more corporate-friendly because they will need jobs after they retire. Again, this is exceptionally implausible. Retired judges will have full-salary pensions and very promising employment prospects should they choose too, and are also unlikely to have many working years ahead of them. Any judge who would be so strongly motivated by such trivial and hypothetical future financial gains would never agree to serve on the Court in the first place.
Levinson is right: life tenure (which, it should be noted, was much less problematic when being a federal judge wasn't a very good job and life expectancies were shorter) involves many costs with essentially no benefits. The country would be better off if it were done away with.
--Scott Lemieux