Comment by balls187

They're not rules. They are laws. US is a Federal Republic. Each member of the federation (aka State) has the right to enact it's own laws, whether they conflict with the Federal Government or not.

And anyone can challenge the legality of a law by filing a suit; then it's left to the courts to ultimately decide whether the challenge has merit or not.

The federal government may not prevail in court, so it exerts it's influence elsewhere, typically by with holding federal funding, or refusing to provide federally backed services.