Drugs are part of every society, consumed for ritual or religious purposes, for pleasure, to enhance athletic performance, or as a means to relieve pain. Throughout the twentieth century, however, an arbitrary and shifting distinction was made between legal drugs that were prescribed and administered by the medical profession, and illegal drugs that were subject to state control and suppression.

Illegal in Canada since 1923, marijuana is the most controversial of illegal drugs. Because it lacks the same addictive and harmful qualities of other illegal substances, such as heroin and...