In 1914 Congress passed the Harrison Narcotic Drug Act, the first measure to control narcotics trafficking. The act approached control through a revenue path—requiring those who transported, sold or possessed narcotics to report it to the Internal Revenue Service (IRS) and pay taxes. The Harrison Act limited opium availability to only small amounts as prescribed by doctors, who were required to register and pay taxes on the amounts they prescribed. The Harrison Narcotics Act is considered to be the basis behind most anti-drug legislation in the United States because it had a major impact on the national and international drug market.