Is there something more that a local municipality can do when it's illegal at the state and national level? I'll admit I don't know anything here. It just struck me as more official than the existing wink and nod.
I suppose it varies. But DAs have wide discretion--strictly speaking, absolute discretion--to abstain from prosecution, and in San Francisco the DA is an elected position, which is common nationwide. (SF also has an elected public defender office, which is extremely rare.) Moreover, AFAIU DAs have some supervisory authority over the police, by law (e.g. investigating misconduct) but mostly by the fact that it behooves the police to have good relations with the DA (and vice-versa). So police aren't in the habit of enforcing specific laws or making arrests that the DA is unlikely to prosecute. And unlike many other cities, the SF DA's office is not very deferential to police department demands--e.g. how to expend their resources to best improve public safety in their opinion--which is often cited as a major reason for supposedly exceptionally low morale among SF police officers.
SF in particular also has a Police Commission, which has direct supervisory authority over the police department, including setting and enforcing policy. Four SF Police Commissioners are nominated by the Mayor, and three by the Board of Supervisors; all must be ratified by the Board of Supervisors. Usually a Police Chief, especially outside major cities, is the top such authority, though the SF Police Chief still has plenty of discretion, and is still appointed by and answers directly to the Mayor.
So in SF both the citizenry via the elected DA, and city politicians via their appointments, control policy regarding if, when, and how criminal laws are enforced. And those are the avenues by which SF has already circumscribed and muted drug laws otherwise beyond the city's control. So the mechanisms are in place, not to mention the actual policies; thus why I called the bill theater. Strictly speaking, though, it has some substance in the sense that it prevents the DA, Police Commission, Mayor, or Police Chief from rolling back existing enforcement restrictions, to the extent they could do so independently.
