“It is going to get incredibly messy and complicated,” Professor Donley said, adding that Justice Kavanaugh’s statement offered “literally no protection” to out-of-state doctors and clinics who provide abortions to women from states where the procedure is illegal.

Justice Kavanaugh’s description of the scope of the right to travel, which responded to a question in the dissent, was oddly limited, said Seth Kreimer, a law professor at the University of Pennsylvania and the author of two foundational law review articles exploring the right to travel in the context of abortion.

The right to interstate travel, he said, “is fairly solidly rooted in constitutional structure and longstanding constitutional practice.” But that is only part of the puzzle.

“Read closely,” Professor Kreimer said of Justice Kavanaugh’s statement, “he may not even suggest protection against prosecuting the resident upon her return — or seeking to sanction doctors in sanctuary states either by prosecution or damage actions.”