A nurse practitioner licensed under title 63, chapter 7, and a physician assistant licensed under title 63, chapter 19, shall have the same authority that a physician has under this part to issue certified statements of disability or deafness to accompany the application of disabled or deaf persons to obtain the appropriate registration, license plates, placards and decals from the department, as described in this part, only if the authority is expressly included in the written protocol developed jointly by the supervising physician and the nurse practitioner or physician assistant, whichever is applicable, setting forth the range of services that may be performed by the nurse practitioner or physician assistant.