Wouldn't that have also gone against his fifth amendment rights? It would seem that he was damned if he did and damned if he didn't.
Capone:
"Well, you see sir, I made five million dollars by selling illegal booze on the black market, but I just want to make sure that I pay my fair share of my taxes on it."
Judge:
"That's great Al. As long as we get our cut, your fine."
Yeah, like that's going to happen. See the problem there?
I stay out of tax policy arguments. I see no future in them. I believe in working on the demand side of the revenue problem.