Duuuuhhhhh....

[sutur]

By law you dont have a licence restriction in US, hence you can buy what you want once you get your licence.... there is no Red/Green P concept

And so it should be. If a fool wants to ride a lethal bike with no training, then so be it.
If a fool wants to ride a motorbike without a helmet, it should be allowed.
I certainly wouldn't recommend it, but I don't think people should be hindered by law to do so.

I don't think a society should bother protecting it's people from themselves, because you have to ask where it ends.