Glenn Reynolds and I have made the same point as Prof. Adler, at greater length.
Outlawing a particular type of abortion procedure simply isn’t within a reasonable understanding of Congressional power to regulate interstate commerce. Partial-birth abortion is horrible, and if I were a state legislator, I would support a state-level ban. But abortion performed within a single state is not “interstate commerce.” Nor is divorce, gun possession, drug possession, most violent crimes, and many other human activities.