It would be almost technologically impossible to enforce in the first place; look at the failed attempt to filter adult content sites and companeis like WebAware which have terrible track records at filtering content for workplaces. No matter how well-designed it is, a piece of software cannot make any sort of meaningful judgement call about sites.
Legally speaking it would also be a failure, as the only way for it to be seriously tabled would be for online gambling to be made illegal entirely. That way ISPs would have something on which to fall back and it would be more difficult for "rogue" ISPs to simply disregard the law, since they themselves could be found legally culpable.
In a perverse sort of way I wish they would make online gambling illegal, ban banks from working with sportsbooks, and ban ISPs from showing gambling sites. The tens of billions of dollars that would be pissed away on compliance for legislation that would ultimately (and probably more rapidly) meet the same fate as Prohibition would maybe ignite a current against so-called "morality" legislation, and we could suddenly dispense with all kinds of stupid shit that the state currently does which has no relevance to good governance.
Phaedrus