I agree with agilebasenji on this one, IMO there is more than enough evidence showing that dogs involved in performance events shouldnt be S/N before their growth plates close. There doesnt seem to be an exemption for this unless you also show the dog, and many people, myself included, have no desire to participate in conformation but enjoy competing in other events.
I also agree with Pat that these types of laws will not solve the problem. The irresponsible people the law targets will simply not follow it just like they dont follow the current laws. I dont know for sure but there is probably a leash law and yet there are packs of pit bulls running around attacking people. Its also illegal to fight dogs yet they think these gang members are going to comply with a mandatory S/N law. The irresponsible owners will simply ignore the new law just like they ignore the current laws and the only people hurt by it are responsible owners and breeders.
The other major problem I have with these laws is how they determine who is eligible for a breeders license and who isnt. Many times the only people able to get them are the commercial breeders, aka puppy mills. Or the license cost so much that it strains the finances of responsible breeders that much more, which just takes money away that they could have put into health testing which all breeds need so desperately. Also many responsible breeders dont breed litters every year, in fact they may go several years in between breedings, so how do the laws handle this?
As its been said before in the end the only solution to the problem will be the education of the public no law will magically fix the overpopulation problem.