No, fair use is possible because of the First Amendment. While it is now adopted in statute, the statute was codifying a Constitutional limit that courts previously found in copyright protection grounded in the First Amendment, not the Copyright Clause.
But, still, yes, determining the scope and applicability of fair use is part of applying the law.
Ah, I had heard of the first amendment thing but I thought it was why government work must be in the public domain (i.e. putting it under copyright would prevent reproduction and therefore infringe first amendment rights).
But, still, yes, determining the scope and applicability of fair use is part of applying the law.