I was not aware of such a decree, so I asked Google AI what its sources were. It said the decree was well known and often cited and gave two specific references. It cited a book on playing card history by one Gertrude Randolph, available in snippet view. I could find no such book on Google or WorldCat. A Gertrude Randolph Bramlette Richards did write Florentine merchants in the age of the Medici, in archive.org; it looks interesting, based on a collection of manuscripts at Harvard since 1927 - but nothing under "Visconti" in the index. She also has another book on the same collection of account records, apparently not online.In 1423, Filippo Maria Visconti, Duke of Milan, issued an ordinance that prohibited gambling games, specifically targeting dice, while continuing to permit board games.
Key Details of the 1423 Decree
Prohibition of Dice: The decree strictly forbade games of chance involving dice, which were often associated with immoral behavior, swindling, and civil disorder.
Allowance of Board Games: While gambling was restricted, board games were explicitly allowed, categorized as acceptable leisure activities for the nobility and upper classes.
Inclusion of Playing Cards: Historical accounts of this 1423 decree note that the list of permitted or regulated games likely included card games, marking an early secular legal stance on playing cards in Milan.
Google AI also referred to "Deutsches Spielkartenmuseum (German Playing Card Museum) publications (referenced as P 35, 37)." All I have is their 1988 catalog, nothing there. So I am stumped.
And does anybody know anything about other specific ordinances or decrees by Filippo Maria, other than the 1420 one we do know, which "forbids anyone to play cards, if not according to the correct and ancient system."