It sounds good on paper but even if Congress passed such a thing, it would never (or rarely) be enforceable. Congress would continue to lie and all they'd have to do was claim it was a matter of interpretation. Just as (you say) Bush isn't a liar because he was only repeating what someone else told him, so would Congress. Or the assumptions changed and the tax went up. Or any number of excuses. Let's not forget the one made famous by Ronald Reagan and copied by so many: I do not recall.