(a) In addition to any other penalty prescribed by law, whoever operates any motor vehicle while knowingly having in the motor vehicle or in his or her possession, a controlled substance, as defined in § 21-28-1.02, except for possession of up to one ounce (1 oz.) of marijuana, shall have his or her license suspended for a period of six (6) months.
(b) This section shall not apply to any person who lawfully possesses a controlled substance, as defined in § 21-28-1.02, as a direct result and pursuant to a valid prescription from a licensed medical practitioner, or as otherwise authorized by chapter 28 of title 21.