From The Washington Examiner:

Some federal courts have dealt with a different firearm age limit, upholding the 21-year-old age requirement for handgun sales by licensed dealers. That rule passed Congress in the Gun Control Act of 1968, long before the AR-15 became one of the nation’s most popular guns, and doesn’t ban young-adult handgun possession.

Michael Connelly, executive director of the U.S. Justice Foundation, a public interest law firm that supports gun-rights advocates, said, “I think an effort to ban people between 18 and 21 from purchasing AR-15s would be vulnerable to a Second Amendment challenge, particularly in light of the current makeup of the Supreme Court.”