Original: The DEA has a registration system in place which authorizes medical professionals, researchers and manufacturers access to "Schedule I" drugs, as well as Schedules 2, 3, 4 and 5.
Simplified: The DEA has a system in place which allows doctors and other people, such as dentists, physician assistants, and nurse practitioners, to prescribe medicines, researchers and manufacturers access to "Schedule I" drugs, as well as Schedules 2, 3, 4 and 5.