Well, Wikipedia says in part, "Specifically, the court found the law similar to the British Stamp Act of 1712 in that it would it suppress free speech through taxation and allowing a similar law would be against the clear Founders' Intent of the Bill of Rights."Grossjean v American press and Minneapolis Star tribune v. Commissioner are the cases that address taxes imposed on a civil right can be unconstitutional.
I suppose it only applies to the 1st amendment. When it's guns then they can tax you; don't like it then you can spend ten years in prison for evading the tax.
In the other case the state of Minnesota demonstrated no such justification to impose a special tax on a select few newspaper publishers. I suppose those people like me are not a "select few".