R.I. Gen. Laws § 31-27-2.4: Driving while in possession of controlled substances.

(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.