Accounts can receive temporary and permanent bans for violating the Game Rules.

You can see the specific paragraph of the End User Licence Agreement (EULA) that served as a reason for the sanction to be applied in the pop-up menu that appears in Game Center upon game launch attempt.

You can find the full text of the EULA and Game Rules, that you accepted upon creating the account, here:
MY.GAMES End User Licence Agreement for Games

Should you require additional information about sanctions, please use this article to submit a ticket from.