Features of a libertarian argument
All human persons possess natural rights.
1) The natural rights to life, liberty, property, and pursuit of happiness are
valuable possessions.
2) Life, liberty, and pursuit of happiness may be regarded as valuable
possessions--that is, property that belongs to each person. In this respect,
property is the basic natural right.
3) All human persons--both strangers and those familiar--are members of
the moral community.
4) The state is a moral entity when it upholds human rights. When the
government leaders fail to uphold them, they may be overthrown.
5) The individual, not the community, is the determiner of the good life.
6) Consent to membership in the state is the motive for following the rules.
7) An individual may consent to a state that is ruled by the majority and
upholds natural rights.
8) An action or policy is wrong if it violates a person’s natural rights.
The central problem with the libertarian approach is a tyranny of the
powerful minority. The “haves” may prosper while the “have-nots” suffer.
 

Mary Ann Warren, "On The Moral and Legal Status of Abortion"

CENTRAL THESIS: The fetus does not possess a right to life.

MAIN SUPPORTING POINTS:
The fetus is not a member of the moral community.

A woman's right to an abortion is unequivocal.

SECONDARY SUPPORTING POINTS:
The fetus lacks all five criteria for qualifying as a person: 1) consciousness,
2) reasoning, 3) self-motivated activity, 4) capacity to communicate, and
5) self-awareness.

The liberty rights of the woman always outweigh the interests of the fetus.

PROBLEM WITH THE LIBERTARIAN POSITION:
A tyranny of the powerful--such as the owners of resouces or property.

RESPONSE TO PROBLEM WITH THE LIBERTARIAN POSITION:
A woman's body is not her property.