R.I. Gen. Laws § 5-20-9: Acts for which journeyperson’s license required.

No person shall engage to work as a journeyperson plumber, journeyperson irrigator, journeyperson water-filtration/treatment-system installer or represent in any form or manner that he or she is a journeyperson plumber, journeyperson irrigator, journeyperson water-filtration/treatment-system installer, unless that person possesses and carries on his or her person at all times while engaged, a certificate of license in full force and effect from the department of labor and training specifying that person as a journeyperson plumber, journeyperson irrigator, or journeyperson water-filtration/treatment-system installer employed by the properly licensed master-permit holder.