If you tell people they cannot do something, particularly if it involves free expression, they will move heaven and earth to find a way around the regulations. Take, for example, the duchies of Schleswig and Holstein, historically caught between Denmark and Germany. The kingdom or country ruling over each duchy changed over hundreds of years through complicated trades and treaties. In 1864, these regions were ceded to joint rule by Prussia and Austria, which is complicated enough, and the residents were forbidden to fly the Danish flag.
Danish farmers in the region then embarked on a project to breed pigs that resembled the Danish flag, which is red with a white cross. They got the vertical white stripe on a red-haired pig with a new breed called the Husum Red Pied (Husumer Rotbunte). Others loyal to Denmark would recognized what the pigs meant while the farmers maintained plausible deniability. Now 150 years later, that region is split between Germany and Denmark, and the Husum Red Pied breed is almost extinct. Read of the rise and fall of the political pig at Amusing Planet.
(Image credit: Axel Krampe)