In 2013, nearly every state in the U.S. required that adults obtain a permit to legally carry a concealed firearm in public. Just four — Vermont, Alaska, Arizona, and Wyoming — didn’t require a permit.

A decade later, the national landscape has reversed: A majority of states have passed laws, known as permitless or constitutional carry, that remove licensing requirements and allow largely unregulated concealed carry.

Permitless carry laws have been a top priority of the firearm industry and gun rights groups, including the National Rifle Association, Gun Owners of America, and the National Shooting Sports Foundation. Proponents argue that under the Second Amendment, Americans should not need government permission to carry a gun in public.

Gun reform groups that oppose permitless carry laws point to research that shows loosening permit requirements may increase homicide rates. Removing permit requirements increases the chances of gun violence, they say, by allowing people to carry guns without training or a background check.

Though most states have permitless carry laws, the majority of Americans live in states that still require a permit or license to carry a concealed firearm. Permitless carry states tend to be more rural and sparsely populated, with some exceptions like Florida and Texas.

While permitless carry laws remove a significant barrier to carrying in public, they do not apply to people who are otherwise prohibited from possessing guns under state or federal law, including for a previous felony or domestic violence conviction. 

Federal background check laws, which require federally licensed gun dealers to run background checks on prospective gun buyers, still apply in permitless carry states. But the vast majority of permitless carry states do not require background checks on gun sales between private parties, so someone could legally purchase and carry a firearm without undergoing a background check.

Permitless carry laws also mean fewer people receive training before carrying in public. Some states — like Florida, Ohio, and Nebraska — required live-fire training before someone could qualify for a permit. But removing the permit process effectively nullifies any training requirement.