As a bit of clarification, Public Law 280 was explicitly not a regulatory or general grant of authority, it is confined to criminal code enforcement. Several states in the wake of PL280 tried a few shenanigans–one State attempted to begin levying State property taxes against tribes, the Supreme Court ruled that PL280 had granted no such authority. California attempted to criminalize Indian gaming, but the court ruled that California’s gambling laws were regulatory and not prohibitory. Meaning–California had not actually banned gambling, it had regulated gambling such that most gambling was not permitted, but because California had allowed one form of gambling to continue–the State run lottery, its gambling laws were a regulatory regime–and PL280 doesn’t extend regulatory regimes over the reservations. If California had implemented a true criminal ban of all gambling (and shut down the State Lotto), then because it is a listed state under PL280, it could have then shut down Indian casinos.
The Indian Gaming Regulatory Act of 1988 which was passed after that case formalized many rules around Indian gaming as it was then becoming a significant issue of concern.
States thus fully banning abortion, that are covered by 280, probably could enforce that inside the reservations. States that simply “regulate” abortion through medical regulations probably would not be able to impose those regulations.
That ties into a large debate about to what degree States can get away with such laws. That is more of an open question, and was discussed extensively here: