A law to control who can and can not have children is the beginning of a dark and dirty road to eugenics. Add to this the fact that, statistically (although the majority of them are not violent unless provoked) 1% of our fellow humans are sociopaths. Studies of sociopaths have shown that they tend to be high intelligence, though they will sometimes put on facades to create the illusion that they aren't, and they are quite attracted to power. That said, it is not at all far fetched to postulate that a sizable percentage of the people who make our laws, are themselves sociopaths. So the sociopaths would be making the laws banning the sociopaths from having children. I can forsee that having some repercussions.
And even if one did put a law in place, and it somehow didn't deteriorate into a state-run eugenic program, how would you identify the sociopaths? Oh sure, we've studied sociopaths plenty, we know behavior like the torture and killing of small animals is a pretty good predictor of people who will grow up to be sociopaths, but unfortunately, it is not generally possible to identify a sociopath until after they have been caught commiting a crime.
The best thing you can do is keep a close eye on these kids, and when shit goes down, you make sure you call the police, and make sure they are punished for their actions. And, if at all possible, make sure you are not discovered as the one who turned them in. Unfortunately, there's not that much else you can do.