I found this anecdote while perusing the NewspaperArchive.com.
State officials who supervise the sale of peddlers’ licenses required by statute today chuckled over an unusual example of commercial enterprise.
Several Wisconsin cities recently adopted ordinances which make it a misdemeanor for itinerant peddling gentry to enter the premises of residents without explicit invitations.
One of the ordinances was adopted by the city of Bloomer, where residents were told to put up signs warning off peddlers.
Promptly, a shrewd peddler came to town to reap a harvest selling cardboard lawn signs reading: “Peddlers and Solicitors Not Allowed.”
From the Appleton Post Crescent, May 30, 1938