Most gifted kids hate following rules when they don't understand the reasoning behind them. Answering with "because I said so" is about as effective as saying "because soup is wet". They need things explained, and often prefer an explanation on an adult level. It sounds like your son is challenging you using "adult" logic, which to me suggests he wants you to discuss your decision in an adult way.
And I'm not a parent, but as a teacher, I figure if I can't adequately explain a rule or decision, I probably didn't have the right to enforce it to begin with.
