That's what laws do: discriminate. "This behavior is not allowed" or "this behavoior is legal." That's what a legal system does.
And that's what's so `topsy-turvy' about this issue.
The feds don't enforce their law (USC Tile 8), so they rule that states and local governments must follow suit.
We've fought over less. Stamps & tea, and over similar disputes: states rights.