Well, I would have to go check, but IIRC a tax as a means of a prohibition is also extralegal/unconstitutional also, regardless of what that Commie said.I believe you are incorrect on this. The .gov has used taxation (tax stamps) to ban/prohibit things. Look at the Marijuana Tax Act of 1937.
It basically states you must have a tax stamp, like the NFA tax stamp, to buy/sell/produce marijuana, but the would not sell anyone the tax stamp.