Reject user from SQL-DB

Hi, I'm afraid I'm currently not seeing the wood for the trees, please help me out. ;-) I'm using stored procedures in MySQL to query for check and reply items for users. I don't need (or want) user groups so there's always a positive Fall-Through attribute returned. There are quite a few possibilities why a user can get rejected: Wrong login, banned from this location, generally blocked, session time/ timespan exceeded and so on... As a result of the information gathered in these stored procedures I know whether the user may connect or not. My question: What attributes do I have to return from MySQL to reject this user??? Am I getting my wires crossed? Thanks a lot! JB