https://www.scientificamerican.com/article/gun-science-proves-arming-untrained-citizens-bad-idea/

Another myth to fall to the facts is that gun-control laws disarm good people and leave the crooks with weapons. Not so, say the Johns Hopkins authors: “Strong regulation and oversight of licensed gun dealers—defined as having a state law that required state or local licensing of retail firearm sellers, mandatory record keeping by those sellers, law enforcement access to records for inspection, regular inspections of gun dealers, and mandated reporting of theft of loss of firearms—was associated with 64 percent less diversion of guns to criminals by in-state gun dealers.”