The 16th, the primary source of legal theft, was never properly ratified. Furthermore, The Constitution contains many loopholes deliberately placed there by the Founding Lawyers. Many of the Revolutionaries, such as Patrick Henry, despised the Constitution.
I'm aware that there is some controversy about that. I'm not sure if the claim is true or not. It seems to me that if it wasn't true, that it would have been disputed before now. It also seems to me that the controversy hangs by one vote. So almost two thirds of the states were in fact for the Income Tax. Nevertheless, that doesn't excuse failure to follow due process, if in fact that is what happened.
But they would have simply raised the money in some other way or the Income Tax would have continued to try to get the Income Tax properly ratified, and it probably would have happened anyway. I'm not fond of the income tax but if it was only one state that is in dispute and that state didn't cry foul at the time, I think the case is dubious.