Mississippi Code Title 63. Motor Vehicles and Traffic Regulations § 63-1-224

(1) A person who holds a commercial driver's license and drives a motor vehicle within this state or a person who drives a commercial motor vehicle within this state for which a commercial learner's permit or a commercial driver's license is required under this article is deemed to have given his consent to a chemical test or tests of his breath for the purpose of determining the alcohol content of his blood. A person may give his consent to a chemical test or tests of his blood or urine for the purpose of determining the presence in his body of any other substance which would impair a person's ability to drive a motor vehicle.

(2) The tests shall be administered, and all procedures and proceedings relating thereto shall be performed, as nearly as practicable, in accordance with the provisions of the Mississippi Implied Consent Law. However, from and after April 1, 1992, refusal of any such person to submit to such test or a test given which indicates that such person was driving such motor vehicle within this state with any measurable or detectable amount of alcohol in his system or while under the influence of a controlled substance shall require such person to be immediately placed out of service for twenty-four (24) hours and shall require suspension of the commercial driver's license of such person for the applicable period of time prescribed in this article.