A legislator shall not be prosecuted or disciplined for a violation of this chapter if his alleged violation resulted from his good faith reliance on a written opinion of a committee on standards of conduct established pursuant to § 30-120, an opinion of the Attorney General as provided in § 30-122, or a formal opinion or written informal advice of the Council established pursuant to § 30-355, and the opinion or advice was made after his full disclosure of the facts regardless of whether such opinion or advice is later withdrawn provided the alleged violation occurred prior to the withdrawal of the opinion or advice.