Cleric changing domains

[GriffinRider]

Just a quick question for you all: I have a cleric in the party who wants to change domains. He's not interested in abandoning his deity; he just wants to drop one of the domains he's chosen for a different one, which is in his god's portfolio. I haven't found anything about whether this is permissible, or if there is a penalty for it. I know my player; he isn't trying to game the system. He just made a slightly less than well-informed choice when he took a level in cleric. Unless there's something clear and severe regarding this, I'm inclined to just let him have this one.

[torrasque666]

As long as its still the same deity, this is covered by the retraining rules in the Player's Handbook II, starting on page 192. They even use a cleric of Heironious swapping Law for War as an example of why retraining might be used.

[Gildedragon]

There's a 2nd level cleric spell that lets one change domains for days/lvl.
Allowing it to be permanent with some downtime or a ritual/incantation (free of cost but for the, say, two day casting time) is perfectly reasonable.

[TaiLiu]

There's a 2nd level cleric spell that lets one change domains for days/lvl.
Allowing it to be permanent with some downtime or a ritual/incantation (free of cost but for the, say, two day casting time) is perfectly reasonable.
Yup! This spell is called Substitute Domain.