It's often said that making abortion illegal won't reduce abortion much because people will be driven to underground abortions, which are less safe and thus cause more damage than legal abortions because they also affect women's health. Suppose this is right (and suppose it didn't contradict the complaint you hear sometimes from pro-choice activists that making abortion illegal will prevent people from exercising what they think is a sacred and fundamental right to kill their fetuses). Does it follow that abortion should remain legal?
Ryan Anderson argues that it doesn't follow [hat tip: Mark Olson], and I think he's right. The argument assumes consequentialism, for one thing, or at least that any non-consequentialist goods will be irrelevant in this issue, and I don't think that's true. The pursuit of justice and punishment of those who are seriously unjust is an important enough consideration that I think the government is violating one of its most basic moral duties if it doesn't have laws against killing fetuses, and that's true even if the consequences of illegal abortion are worse than the consequences of legal abortions.
But Anderson also points out some problems with the assumption. If Roe is ever overturned, and states enact different laws on abortion, you might find underground abortions in states where abortion is illegal, but underground abortions aren't going to be a matter of course in states where abortion is illegal if it's not that hard to go across the border and get a legal abortion. It may have an effect on people without the resources to get somewhere, but those aren't the people who could pay for an underground abortion either. Also, I don't see why it should be considered an injustice against the poor simply because other people can get away with evil when they can't; it's not fair, but I wouldn't say an injustice is committed against me if I'm not allowed to rape someone when someone else is. Remember that this is supposed to be an argument to convince pro-lifers to prefer to keep abortion legal, so we have to assume, even if just for the sake of argument, that pro-lifers are correct in seeing abortion as immoral.
One other things is noteworthy about his response. He notes an eerie parallel with the kind of reasoning used by the defenders of slavery against abolition. They argued, on consequence-based grounds, that releasing slaves would be bad for the slaves. But this seems to be one case where it's very clear that there's a moral obligation to release them (and for those who put them in this position to expend a lot of resources ensuring that the consequences for them wouldn't be bad, although I don't see any parallel here unless the abortion industry can figure out how to resurrect dead fetuses). Isn't the same true with abortion, if the pro-lifer is correct that abortion is immoral?