If he gave up the spellcasting (never learned it at all in the first place), then what happen to the Spellcraft Skill? What would take its place if applicable?
He can keep the skill. It means he doesn't know how to cast spells, but understands the principles of the skill. He can identify them as well as magical effects, but never trained to wield such magic himself. No need to drop it, though it may not be as useful.