R.I. Gen. Laws § 5-20-8
No person shall engage in this state in the business of plumbing as a master plumber, or irrigation as a master irrigator, or commercial water-filtration/treatment work as a master water-filtration/treatment-system installer; or as an employer of a journeyperson plumber, journeyperson irrigator, journeyperson water-filtration/treatment-system installer or plumber's apprentice, or apprentice irrigator, or apprentice water-filtration/treatment-system installer; or enter into contracts or agreements for the installation, maintenance, or repair of plumbing or irrigation systems or water-filtration/treatment systems; or perform any of the acts specified in this chapter for performance by a master plumber, master irrigator, or master water-filtration/treatment-system installer; or advertise or represent in any form or manner that they are a master plumber, master irrigator, or master water-filtration/treatment-system installer; or that they will install plumbing, irrigation systems, or commercial water-filtration/treatment systems, unless that person possesses a certificate of license in full force and effect from the department of labor and training specifying that person as a master plumber, master irrigator, or master water-filtration/treatment-system installer. That person shall carry the certificate on their person at all times while so engaged, and shall affix their plumber's license number or master irrigator's license number to any contract they execute or bid filed with any person for their professional services and to any applicable permit required for the performance of those services.
R.I. Gen. Laws § 5-20-8