United States v. Linder
In Linder v. United States, 268 U.S. 5 (1925), the U.S. Supreme Court reversed a conviction of a physician for violating laws against narcotics. The Court found a lack of authority for the position that a physician acting in good faith and pursuant to fair medical standards may be convicted for giving moderate amounts of drugs to a patient to relieve drug addiction problems.
This precedent is often cited for its statement that "[o]bviously, direct control of medical practice in the States is beyond the power of the Federal Government." 268 U.S. at 18.