Nothing is stopping it, just need folks who know how to conduct a fox hunt, and catch the people doing the jamming in the act, and the FCC will do something with proof.
Last time it happened, a group of HAMs held a fox hunt, found the fellow (just one) who was doing the jamming, and warned him to stop, they had video evidence of him doing it, and a video of him admitting to do it.
He has since not been on the air as far as I know, haven't looked to see if the FCC yanked his GMRS license or not.