I thought the Constitution is "where the buck stops", the Supreme Law. It takes precedent over any law, legal theory, precedent, tradition, etc.

The first amendment, as written, outright "enjoins" Congress from creating any "exceptions" or define what kinds of speech are actually protected.

I also think the Constitution provides one, and only one way for Congress to modify the 1st amendment so there can be categories of speech that can be "abridged": a constitutional amendment.

So, which kind of legal maneuvering, or reasoning as been used to somehow justify the amending of the 1st amendment without actually amending it?