
It means that there can be limitations on Constitutional Rights in order to keep people safe. Justice Scalia wrote this in the D.C. v. Heller Opinion. There are also limitations on free speech. You can’t yell “fire” in a crowded room nor can you burn draft cards because of the O’Brien test
Well there are already limits. For example convicted felons can’t possess a firearm and red flag laws prevent certain people from possessing as well. But I also think there should be mandatory licensing and training as long as it is easy, accessible, lawful, and avoids undue burden. In fact, states that implemented those measures have actually seen a reduction in both firearm homicide and s**cide rates.