If it is claimed that a person has engaged in conduct which could be subject to an order by the Attorney General or by a court, the Attorney General may accept an assurance in writing that the person will not engage in the conduct in the future. Such assurance of voluntary compliance shall not be considered an admission of violation for any purpose, except that if a person giving such assurance fails to comply with its terms, the assurance is prima facie evidence that prior to such assurance he engaged in the conduct described in such assurance.