Laws against robbery did not stop them either. Hell, EVERY law has been broken at one time or another; since breaking the law proves it restricts freedom without preventing crime, we should remove them all. *nods*

The point is not preventing all crime, but a far more complex multilevel one. First, it REDUCES the applicable crimes impairing the means and opportunity to commit them, thereby diminishing motive. Criminalizing the means for those with criminal history/proclivities allows their arrested the moment they are caught with a gun even if they have not yet committed OTHER (violent) crimes with it. Registration helps cops identify stolen guns before they are used in crimes. Even when those stopgaps fail to prevent gun violence, the ability to stack a half dozen charges on the perpetrator helps keep them in prison for an extended period even if they "only" kill one or two people instead of dozens. Mass shootings get the headlines, but liquor store robberies kill far more people.

In the case of mental health screening, gun control aids diagnosis, and therefore treatement, of dangerous mental illness, again before anyone is harmed. Not everyone who shoots people is a "bad guy" who will always get a gun and thus needs to a citizen-hero to shoot them. Many are just very mentally unstable people who do not need to be shot or possess anything more lethal than safety scissors, but do need medical supervision.

Of course, some aspects of gun control are not aimed at crime in ANY way. Mandatory training and certification is not designed to prevent crime, but accidents and misuse, which are common and dangerous with untrained gun users. When gun control advocates lament children finding their parents gun and injuring or killing themselves or others, gun rights advocates angrily and rightly respond that the parents should not have made the gun so easily accessible—it sure would be nice if someone mentioned that to the parents BEFORE their children grabs their gun. Now, you might say no one should need to be told something like that, but then we are back to "mandatory screening, training and certification for gun ownership."

There is FAR more to this than "laws intrude on personal freedom without preventing crime, therefore they are ineffective infringements we should repeal."