Michigan Law
According to current Michigan law, you do not have to maintain a license to practice:
(b) The affectation of the human energy system or acupoints or qi meridians of the human body while engaged within the scope of practice of a profession with established standards and ethics and as long as those services are not designated or implied to be massage or massage therapy. These practices include, but are not limited to, all of the following:
(i) Polarity or polarity therapy.
(ii) Asian bodywork therapy.
(iii) Reiki.
(iv) Shiatsu.
As far as I am aware, this also indicates (by omission) Reiki practitioners do not need to be ordained or in the health-care field.
National Acknowledgement
Federally, Reiki practice is acknowledged through the National Center for Complementary and Alternative Medicine. According to the “Training” subset their Reiki introduction:
Training “There are many different forms of Reiki, and no special background is needed to receive training.”
This is as close as they get to mentioning any sort of extra qualifications regarding Reiki and this is only from the training perspective. Alternatively, when addressing another more interventionist therapy such as Acupuncture, NCCAM states:
Finding a Qualified Practitioner
Check a practitioner’s credentials. Most states require a license to practice acupuncture; however, education and training standards and requirements for obtaining a license to practice vary from state to state. Although a license does not ensure quality of care, it does indicate that the practitioner meets certain standards regarding the knowledge and use of acupuncture.
This leads me to believe if there were standards of qualifications for Reiki practice, they would have included them in the overview as with the overview on acupuncture.