Then they need to secede from the Union. US Constitution claims it is the "Supreme Law of the Land". If Denver doesn't like it, there is a mechanism for them to withdraw. It's a bit broken, due to the Civil War, but times are different. They might just succeed in seceding.
Suits me, the place is a cesspool. I won't go there or patronize any buisness there. I tell merchents that, I won't pay taxes to support that town. Too bad I have to miss the Sportsmans Exposition again, though.