(a) Notwithstanding any other provision of law, a principal campaign committee or political action committee may return or refund, in full or in part, any lawful contribution it receives to the donor, provided that such return or refund may not exceed the amount received. Any lawful contribution refunded to the donor must have been reported in an itemized manner and the refund shall be itemized in the report for the period in which the refund is made. In the case of a political action committee, the refund shall occur within 18 months of the date of the contribution; provided, however, that if the refund of the contribution is required by law or regulation, then the 18-month time limitation shall not apply.
(b) Notwithstanding any other provision of law, a principal campaign committee or political action committee shall promptly return or refund, in full, any unlawful contribution. It shall be unlawful for any person acting on behalf of a principal campaign committee or political action committee to retain or cause to be retained a contribution that the person knows or reasonably should know was made in violation of this chapter. It is a defense to prosecution that the unlawful contribution was returned or refunded in full within 10 days of the date the contribution was made.