The General Law Amendment Act, number 37 of 1963 (commenced 2 May), commonly known as the 90-Day Detention Law,[1] allowed a South African police officer to detain without warrant a person suspected of a politically motivated crime for up to 90 days without access to a lawyer.

The Amendment Act also introduced the so-called "Sobukwe Clause" which allowed people already convicted of political offenses to be further detained (initially for twelve months).

This Act strengthened previous amendments by further defining political crimes under Apartheid.

Section 5 of the Act made a capital crime out of "receiving training that could further the objects of communism or advocating abroad economic or social change in South Africa by violent means through the aid of a foreign government or institution where the accused is a resident or former resident of South Africa".

The legislation made provisions for imposing "sentences ranging from a minimum of five years imprisonment to death for anyone leaving the country to learn sabotage techniques, for advocating the forcible overthrow of the government or for urging the forcible intervention in domestic South African affairs by an outside power, including the UN".