The Anarchical and Revolutionary Crimes Act, 1919, popularly known as the Rowlatt Act or Black Law, was a legislative act passed by the Imperial Legislative Council in Delhi on March 18, 1919, indefinitely extending the emergency measures of preventive indefinite detention, incarceration without trial and judicial review enacted in the Defence of India Act 1915 during the First World War. It was enacted in light of a perceived threat from revolutionary nationalist organisations of re-engaging in similar conspiracies as during the war which the Government felt the lapse of the DIRA regulations would enable.
Passed on the recommendations of the Rowlatt Committee and named after its president, British judge Sir Sidney Rowlatt, this act effectively authorized the government to imprison any person suspected of terrorism living in the Raj for up to two years without a trial, and gave the imperial authorities power to deal with all revolutionary activities.
As per this Act, any person could be arrested on the basis of suspicion. No appeal or petition could be filed against such arrests. This Act as called the Black Act and it was widely opposed.