It is illegal to use on the street, and it is illegal to fill a car from the pump, but there is nothing to stop you from buying a drum of it, or getting a drum filled with it, and putting it in your car later on.
The thing i would be making sure of first is that it is 100% unleaded avgas that you are putting in, there is different types, im pretty sure that most of them are mostly unleaded now, but if there is lead in it, then it will destroy your catalytic converter very quickly.
Red EA Fairmont Ghia
Straight Gas Turbo'd at 15PSI, and happy for now.
Water to air intercooled
Sitting on koni and kings combination