Todd Zywicki points to a study that concludes that mandatory waiting periods for abortion reduce suicide rates after unplanned pregnancies. I haven't looked at the study itself, but some of the comments on Todd's post seem to me to be unjustifiably critical. In particular, they claim that a libertarian view of the purpose of law wouldn't allow the kind of paternalism that such laws are based on. I think this is completely wrong.
The libertarian argument fails for a number of reasons (including that libertarianism is wrong), but the most notable is that this isn't paternalism in the ordinary sense. Paternalism is usually thought of as government interference in people's decision-making process when someone has legitimately consented to a practice that the government is rejecting as legitimate consent for no reason other than that they consider such consent irrational. Requiring motorcycle helmets would be such a paternalistic law. We don't, however, consider it paternalistic to restrict a four-year-old from doing things that it takes an adult understanding to consent to. By the same reasoning, we don't consider someone to have consented to sex if under the influence of a mind-altering drug. Waiting period laws are a simple step further in the same direction. Someone who has just found out she is pregnant will not be thinking as rationally as someone forced to wait 24 hours before making an irrevocable decision. For the same reason that euthanasia advocates insist that some time be taken before considering someone to have consented rationally to being killed, those who favor waiting periods for abortion think rational consent requires taking some time before having an abortion. This seems not only eminently reasonable to me but perfectly consistent with a libertarian view of the purpose of law.