Mouseferatu said:I wouldn't punish him at all. I would, however, start sending him hints that something is seriously wrong, and his attention is required immediately. If he fails to act once the hints have gotten strong enough, then punish him.
Can I add to the chorus of voices agreeing with Mouseferatu. That is exactly what should be done, not punishing the paladin unfairly but giving him a chance to correct his mistake as well as creating good roleplaying opportunitys and a new plot line for the party to focus on.