Came across something Palm Beach does...

In an effort to control people sending out anonymous mailings during campaign and election periods, the Town of Palm Beach passed the above resolution in 2009. The can't do more than "condemn" the practice and then direct people to make their own complaints to the Florida Commission on Ethics for violation of election laws, which include anonymous mailings. They publish the resolution every time that they have a local election.

Not sure how effective this is. I do know of some instances where people have sent out blanket mailings that couldn't be sourced. Of course, these do not have the required disclaimer. Don't get any ideas!