1) Some comments here seem to assume CA has proposed paying salaries to players. It has not. The new law would allow players to collect money from endorsements--think appearing in ads for Nike or Gatorade. Not many players will have this opportunity--we're mostly talking about a handful of basketball or football players in top-tier programs. There also could be some chances for other athletes to appear on billboards for a local car dealership or local cable TV ads for a restaurant--these won't pay much compared with having your name on a shoe, but the money could be meaningful to a full-time college student. You may oppose what California has done, but they aren't calling for schools to pay players.
Given the billions of dollars sloshing around college athletics, I'm not opposed in principle to letting athletes earn what the market is willing to pay them. That's capitalism. My main concern is the opportunities for corruption this will introduce. Maybe there is little actual value to a car dealer to putting a particular college linebacker's face on a billboard; but if the dealership owner is a booster, he can pay that player (many) thousands of dollars and call it an endorsement deal. I see no effective way to police that kind of arrangement. (Even so, I'm not convinced the CA legislation is a bad idea. Something needs to change in college sports.)
2) If CA is the only state to enact such a law, then the NCAA holds all the cards here. Within days of an announcement that Stanford, USC, UCLA, etc. can no longer play against NCAA programs, California legislators will be deluged with calls from angry alumni. BUT, if other states go along, at some point the NCAA loses this option. Maybe fans in other states would tolerate eliminating California teams (in theory--I doubt it would actually come to that), but if five or six large states' schools also would have to go, that's another story. I make no predictions, but the Tampa Bay Times reported this morning that a Florida legislator plans to introduce California-style legislation in the next session, which begins in January. This issue isn't going away any time soon.