Child access prevention laws (CAP) make it illegal for an adult to keep unsecured guns in a way that a child could access and fire it. There is no such law at the federal level in the U.S., though at least half of states have some version of this regulation.
According to the Giffords Law Center, only two states require unattended guns to be locked at all times: Massachusetts and Oregon. Five other states require guns to be safely stored around people ineligible to possess guns, including children: California, Colorado, Connecticut, Delaware and New York. Eighteen other states and Washington, D.C., impose civil or criminal penalties if a child is able or likely to gain access to a firearm; gains access to a firearm; or uses a firearm to injure or kill someone.