https://www.lewrockwell.com/2012/07/laurence-m-vance/libertarianism-and-abortion/
...I have argued that because the non-aggression axiom is central to libertarianism, and because force is justified only in self-defense, and because it is wrong to threaten or initiate violence against a person or his property, and because killing is the ultimate form of aggression that, to be consistent, libertarians should be opposed to abortion.
...
Why should it be considered libertarian to kill a baby in the womb or unlibertarian to oppose such killing? And even worse, why would a libertarian say that it was unlibertarian to advocate killing foreigners in an aggressive war but not non-libertarian to kill a baby in the womb?
Killing someone is the ultimate form of aggression. Especially a helpless, defenseless fetus that is only guilty of suddenly waking up in a womb. The fetus certainly had no control over being a parasite, aggressing against a woman, invading a woman’s body, or adding unwanted pounds to his host – but its mother certainly did. If an unborn child is not entitled to protection of life, then to be consistent, libertarians should have no problem with the abortion of a fetus from one month old to nine months old. The nine-month old fetus is no more viable than the one-month old one. In fact, a one-month old baby has the same degree of viability. I hate to be so crude, but leave all three of them unattended on a table in a hospital and see what happens.
Why should it be considered libertarian to kill a baby in the womb or unlibertarian to oppose such killing? This has nothing to do with giving the government greater control over a woman’s body; it has everything to do with preventing aggression and protecting innocent life.
If Roe v. Wade were overturned and abortion laws were once again made the provision of the states, there would be nothing unlibertarian about supporting state laws making abortion a crime just as laws against murder, manslaughter, and wrongful death are considered legitimate actions of the states.