Opening a mahjong shop itself is not illegal, refers to the normal charge for playing cards to use, if it is with the mass gambling nature of the activity violates the law.
According to "the supreme people's court, the supreme people's procuratorate on the handling of gambling criminal cases on the specific application of law on a number of issues of the interpretation of" article 9: not for profit, with a small amount of property to win or lose entertainment activities, as well as the provision of chess and card rooms and other entertainment venues to charge only the normal place and service fees for the operation of the behavior, etc., not to be punished as gambling.