Ephedrine Synthetic sources
Most of the L-ephedrine produced today for official medical use is made synthetically as the extraction and isolation process from Herba Ephedra is tedious and no longer cost effective.
Through oxidation, ephedrine can be easily synthesized into methcathinone. Ephedrine is listed as a Table I precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.
The biosynthesis of ephedrine - ResearchGate
Laboratories in many places, notably throughout the USA, are engaged in clandestine manufacture of methamphetamine. The chemistry is well understood, and widely published, notably on the web, though not easy to achieve. It is the synthesis of methamphetamine that is illegal. Two methods that have been described both involve the reduction of ephedrine (itself readily available) using either lithium in liquid ammonia as the reducing agent, or else red phosphorous and iodine to generate HI for the reduction.