So it seems that "many cities have a provision prohibiting discussion of closed session matters," in their ethics policies, but theses provisions "have no teeth."

Responsible stewardship of public information that might compromise a governmental interest should be sufficient to address the city's concerns.

With rare exception, it has been sufficient through the years. Perhaps this is why the open meetings law itself is silent on the issue.

And surely existing ethics policies are broad enough to address a public official's conduct in the event s/he exposes the agency s/he serves to liability or undermines the public's interest.