Licensure. Health care professionals who are employed by the IHS are required to be licensed, registered, or nationally certified. Physician Assistants employed by the IHS must be nationally certified (unless exempted). The IHS does not require PAS to be licensed in the State(s) in which they will be performing their official duties. Based upon Federal sovereignty and supremacy principles, a State may not require that an IHS employee who provides health care within the State as part of his or her Federal duties be licensed in that State. However, Drug Enforcement Administration regulations require the PA be authorized to prescribe controlled substances by the jurisdiction (e.g., State) in which he/she is licensed, registered, or otherwise specifically recognized to practice his/her profession. (See Section G. Prescribing Privileges herein.)