Regulating is not prohibiting. Period. End of story.
Well, we've agreed that the definition of "to regulate" includes "to prohibit" -- therefore, to regulate trade between the states includes prohibiting trade.
Unless you're trying to tell me that "to regulate" has three different meanings when used in the same sentence.
"Regulating is not prohibiting."
Correct. Regulating means a number of things, including prohibiting.