[mpyne]

If they meant to limit it only to keep the states from taxing each other then that's exactly what would have been in the Constitution. For instance Art. I. Sect. 10 is very clear about how states may impose duties and tariffs on imports/exports, it was very much not left to chance.

Knowing the intent of a given clause is helpful for the courts in determining how to interpret the law or Constitution when the written text of the same is unclear. But when the Constitution or law is perfectly clear then that's what the law is.

In this case the relevant clause is "The Congress shall have the Power to regulate Commerce with foreign Nations, and among the several States."

That's it... unlike Art. I. Sect. 10, there are no specific constraints or restrains embedded there, certainly nothing about taxes (since it would be easy enough to simply declare that states could not tax each other, similar to how Art I. Sect. 10 does it).