The gods have a little bit more wriggle room than just granting or deny spells, but that's not really significant here. For a non-divine follower, they would very unlikely do anything at all, unless we are talking about greater offenses, like an Aeridinite suddenly becomming a mass-murderer or something!
Then, the said deity could simply use the tools he has... and guess what that is?
Yes! Clerics, paladins and champions!
But that... eh... that's of course a danger one always has... regardless of whether you are a follower of the deity or not... Being one though, is naturally lowering the threshold level when the deity will act against you... which would still remain very high!