In states that have so-called right-to-carry laws, anyone who is allowed to own guns and meets the necessary conditions can also get a concealed-carry permit.
Many people have argued that right-to-carry laws deter crime because there could be more armed people around to stop a shooter. Though that idea was supported by a controversial 1997 analysis, recent and more thorough analyses have found the opposite effect.
One recent study found that such laws increased the rate of firearm homicides by 9% when homicide rates were compared state by state. That could be because confrontations were more likely to escalate to involve guns or because there were more guns around that could be stolen. Other factors could also be at play.
A spike in gun purchases after the 2012 shooting at Sandy Hook Elementary School led to an increase in accidental gun deaths, especially among kids.
Research has found that when people are around more guns, they're more likely to end up dying from accidental shootings.
After a 20-year-old man killed 20 children and six adults at Sandy Hook Elementary School in Newtown, Connecticut in December 2012, there were calls for legislation that would limit some people's access to firearms. That push resulted in what's now become a predictable phenomenon after shootings: people bought lots of guns.
With more guns around in the months after the school shooting, the rate of accidental deaths related to firearms rose sharply, especially among children, according to a recent study published in the journal Science.
The researchers' calculations showed that 40 adults and 20 children died as a result of those additional gun purchases.