You don't need any licenses to own these magazines. In some places its simply outright illegal to own one, Kookifornia comes to mind. In the free world ( the states in between the coastal states) they are perfectly legal to own. The catch is that they are illegal to manufacture and have been since 1994. If you can find a 50 round magazine for a 10/22, and good luck finding one, you'll pay 2-3x as much as your rifle is worth for the magazine.