The United States Supreme Court has ruled that people who use cannabis for medical purposes to relieve chronic pain are breaking the law.
The decision, by a six to three majority of the judges, means the federal government can enforce a law that outlaws the cultivation and use of cannabis even where it is legal under state law.
At least nine American states allow the medical use of the drug.
Federal government lawyers argued that it would be difficult to enforce the nation's drug laws if there was an exception for medical cannabis.
