Art VI, para 2...,
This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to Contrary notwithstanding.
I'm no great connoisseur of the law or anything, but that sure sounds like a "prohibition" to me..
You're right... You are no connoisseur of law. It is NOT a prohibition of what we are talking about -- civil liberties and such. It does not, for example, prevent a state from establishing a church or engagin in censorship. Sorry.