If you sell a flag that has anything painted or written on it you will be fined.
In Sweden there is a law that forbids you to paint or write anything on a swedish flag. If you paint paint or write anything on a swedish flag its not considered to be a flag anymore. If you sell a flag that does not “obey” this law you will be fined a 100 kr (12 USD). The law is called Flagglagen and the number of it is 1982:269.