On approval

Kevin Drum complains that "[H]aving already decided that injured patients can't sue medical device makers, the Supreme Court is likely to extend that ruling to apply to makers of prescription drugs too". Call me a crazy libertarian, but shouldn't regulatory approval get you a pass on lawsuits? I mean, obviously, if you mislead the Feds, you should be subject to criminal prosecution. But I don't understand quite why FDA approval of drugs and medical devices hasn't long provided legal safe harbor for their manufacturers. The defects that show up, such as the Vioxx and Fen-Phen problems, are discovered long after approval precisely because they're so rare that they don't show up in ordinary clinical trials. If the government experts, who are presumably highly motivated to avoid catastrophes, can't spot the danger, why do we expect the drug companies too?