The principal rationale for certification and licensure is to ensure a minimum level of competency for all health professionals subject to such requirements. All states retain the authority to establish licensure or certification standards for a large variety of health professionals. In contrast to other domains of regulation, the federal government has never threatened to preempt or compete in this domain of regulation. There are three types of professional licensure used for health professionals: a) mandatory licensure; b) certification; and c) registration. The Duke Center for Health Policy has developed a draft working paper assessing the costs and benefits of professional accreditation and licensure and of Medicare conditions of participation (pdf).