Abstract: When a resident of an anti-abortion state goes to a prochoice state to get an abortion, which law applies to that person? To the abortion provider? To anyone who helps them obtain the abortion? Since Dobbs v. Jackson Women’s Health Organization overruled Roe v. Wade, states have passed conflicting laws regarding abortion, and courts will need to determine whether anti-abortion states can apply their laws to persons or events outside their territory either through civil lawsuits or criminal prosecution. This article canvasses the major disputes likely to arise over conflicts of abortion law and the arguments on both sides in those cases. It addresses both common law analysis and the constitutional constraints on application of state law under the Full Faith and Credit Clause and the Due Process Clause, and it comes to some conclusions both about what laws should apply in different fact settings and how the choice of law analysis should proceed.Since Dobbs focused on the “history and tradition” behind rights under the Due Process Clause, and because the constitutional test for “legislative jurisdiction” that regulates when a state can apply its law to a controversy is partly based on the Due Process Clause, we start with the prevalent approaches to conflicts of law available to judges at the time the Bill of Rights was adopted in 1791 and when the Fourteenth Amendment was adopted in 1868, focusing on the “comity” approach championed by Justice Joseph Story. We consider also the First Restatement’s vested rights approach in vogue between the end of the nineteenth century and the middle of the twentieth century. We then move to modern choice of law analysis to determine which law applies when a person leaves their state to obtain an abortion. We will consider the Second Restatement’s “most significant relationship” test, the “comparative impairment” approach, the “better law” and “forum law” approaches, as well as the emerging Third Restatement of Conflict of Laws rules being drafted right now by the American Law Institute.One set of cases involves conduct that is wholly situated within the borders of the anti-abortion state. That state has full authority under the Constitution to regulate its internal affairs and to apply its laws to people who distribute or use anti-abortion medication there or who otherwise assist residents in violating its laws prohibiting or limiting access to abortion. Anti-abortion states have full authority to regulate conduct within their borders. However, the First Amendment protects people who provide information about the availability of abortion services in other states where it is legal, and the constitutional right to travel should protect those who transport someone out of state to get an abortion in a prochoice state or who subsidize the cost of such out-of-state travel.A second set of cases concerns cross-border torts where conduct in a prochoice state has effects in an anti-abortion state. Courts traditionally apply the law of the place of injury to those cases if it was foreseeable that the conduct would cause the injury there. But there are traditional exceptions to the place of injury rule that should apply in the abortion context when the place of conduct defines the conduct as a fundamental right and immunizes the actor from liability or places a duty or an affirmative privilege on the abortion provider to provide the care. Courts should depart from the place of injury rule in those circumstances when conduct is wholly confined to the immunizing (prochoice) state, and that means that an anti-abortion state cannot legitimately punish an abortion provider in a prochoice state who provides care there in reliance on rules of medical ethics that require the care to be provided. Nothing would violate rule of law norms more severely than placing a person under a simultaneous duty to provide care and a duty not to provide that care. On the other hand, anti-abortion states have full authority to regulate out-of-state conduct that does spill over the border into the anti-abortion state, such as shipping abortion medication to a recipient there. Difficult issues of foreseeability and proximate cause arise when an abortion provider prescribes abortion medication in a prochoice state but knows or suspects that the patient will be taking the medication back to the anti-abortion state to ingest. In some fact settings, the foreseeability issue is significant enough that it may rise to a constitutional limitation on the powers of the anti-abortion state to apply its law to out-of-state conduct or to assert personal jurisdiction over the abortion provider. In other cases, the place of injury has the constitutional authority to apply its law to out-of-state conduct that the actor knows will cause unlawful harm across the border but it may or may not have personal jurisdiction over the nonresident provider.A third set of cases involve bounty claims, tort survival lawsuits, or wrongful death suits that an anti-abortion state might seek to create by giving claims to one of its residents against the resident who left the state to get the abortion. Such cases may be viewed as “common domicile” cases by the anti-abortion state since both plaintiff and defendant reside in the anti-abortion state. That may tempt the anti-abortion state to apply its laws to an abortion that takes place in another state even though both conduct and injury occurred in a state that privileges the conduct and immunizes the defendant from liability. However, the law of the place of conduct and injury should apply in those cases since the prochoice law is a “conduct-regulating rule,” and choice of law analysis, traditional rules, and constitutional constraints on legislative jurisdiction all require deference to the law of the prochoice state in such cases. Courts sometimes apply the law of the common domicile when the law at the place of conduct and injury is not geared to regulating conduct there, but the opposite is true for laws directed at conduct, and this article will show why prochoice laws that define abortions as a fundamental right are conduct-regulating rules. The same is true for the question of criminal prosecution. An anti-abortion state has no legitimate authority to punish a resident who leaves the state to get an abortion in a state where abortion is protected as a fundamental right.