In this case, via a law that required all abortionists to have hospital admitting privileges at a local hospital. By throwing up obstacles, even fairly small ones, you reduce the initiative and energy of the targeted group. This is part of the total cultural warfare strategy that I've advocated here at the Chariot. It may well be the best strategy to throw out an insane amount of small obstacles and hindrances, rather than go for figurative instant decapitation.
Attack whenever and wherever the correlation of forces favor your side, against targets dear to the other side. It really doesn't matter whether admitting privileges matter much or what the particular club you're using to beat the other side with happens to be. Until you can reward your friends and punish your enemies, you will continue to lose the cultural war.