Do you have a better word for localities whom do not have the authority to make something legal to effectively do so by directing law enforcement and prosecutors to not pursue a certain offense?
https://www.vox.com/identities/2018/8/20/17938358/marijuana-...
No, that'd be outright legalization.
"Decriminalization" would be instructing law enforcement to not ever enforce a law - stronger than deprioritizing, but weaker than legalizing.
It could also include not explicitly criminalizing or legalizing something (that is: Denver could simply not mention psychedelic mushrooms at all), but in this case there's already a higher-level jurisdiction (i.e. the United States) that does explicitly criminalize it, so a lack of specificity would in this case just mean criminalization.
"Decriminalizing" just means the local police will not enforce the law as written, and if the state or Feddy'Gov doesn't like it then they can send state troopers or DEA agents to hang out on every block in Denver to make sure the law gets followed and shroomers get nailed. Contrary to popular belief, the FBI and DEA don't have unlimited resources, and have bigger fish to fry... so nothing happens most of the time.
In the event the local Denver cops do nail you with shrooms, instead of enforcing the law they'll nail you with a fine or something. No idea what the CO State Troopers are up to, or if they'll be acting in Denver against the decrim bill.
You might still have to pay a fine like a traffic ticket, but it's not a criminal charge or an arrest.
It's also still illegal to purchase but you won't be charged for doing so.
Also, a city has no ability to decriminalize something, as that would have to be done by the state legislature or a statewide vote. So this is really not “decriminalizing” at all... the initiative itself uses the word “deprioritize”: https://static1.squarespace.com/static/5bb4f9c27046803ce123a...
Edit: word choice.