I've avoided starting any abortion debates on this site for several reasons - the best of which is that I can't have babies.
But while doing a bit of websurfing tonight, I found a blog called Libertarians For Life , whose stated goal is "presenting the pro-life case to libertarians, and the libertarian case to pro-lifers."
Their argument goes as follows:
1. Human offspring are human beings, persons from conception, whether that takes place as natural or artificial fertilization, by cloning, or by any other means.
2. Abortion is homicide -- the killing of one person by another.
3. One's right to control one's own body does not allow violating the obligation not to aggress. There is never a right to kill an innocent person. Prenatally, we are all innocent persons.
4. A prenatal child has the right to be in the mother's body. Parents have no right to evict their children from the crib or from the womb and let them die. Instead both parents, the father as well as the mother, owe them support and protection from harm.
5. No government, nor any individual, has a just power to legally "de-person" any one of us, born or preborn.
6. The proper purpose of the law is to side with the innocent, not against them.
I learned my response to the abortion issue from Big Daddy John Spivey - It's a 10th Amendment issue that should be left to the states, and no government (i.e. taxpayer) money should ever be used to fund abortion.
But these folks are making a liberty-based argument about the issue.