I don't think it's accurate to say that most states require a license just to own a firearm. There are age, mental health, and criminal background restrictions, but that's not quite the same thing. Some states do have gun ownership licenses, but most only require licenses to carry a firearm, and in many of those states, that is technically only required for concealed carry.
Amend "most" with many. A quick scan of wikipedia suggests there are about 20 states that require a permit to purchase or registration of ownership. Federal law also restricts ownership by convicted felons in all 50 states which is essentially the same thing - regulation by any other name.
