The fact that criminals who want to have guns will go to extreme lengths to obtain one proves that. Prohibition, in any form, never works. You are simply creating a black market for the prohibited item.
Once you account for gang violence in major U.S. cities, the U.S. is the safest place on Earth. In those 5 counties, gangs operate in areas where guns are strictly prohibited. Not prohibited for them, because their criminals and don't care about gun laws. It is prohibited from law abiding citizens who want to own a tool to aid them in self defense.
https://www.washingtontimes.com/news/2017/apr/25/most-murders-occurred-in-5-percent-of-countys-says/