Some of them are, and some of them are not. Reiki regulated state by state as a medical medium, however, it is not highly monitored. Individuals do not need a license or certificate of coursework to practice Reiki effectively once they have been trained in the art, however, most states require it. You can find out more by following this magical link if you are inside the United States!
Personally, I am certified in Usui Reiki levels I, II, and III, enabling me to treat myself, others, as well as attune others to Usui Reiki.