The Ato Institucional Número Cinco – AI-5 () was the fifth of seventeen major decrees issued by the military dictatorship in the years following the 1964 coup d'état in Brazil. Institutional Acts were the highest form of legislation during the military regime, given that they overruled even the highly authoritarian Constitution, and were enforced without the possibility of judicial review. They were issued on behalf of the "Supreme Command of the Revolution" (the regime's leadership). By suspending habeas corpus, the AI-5 enabled worst of the human rights abuses of the military dictatorship.
AI-5, the most infamous of all Institutional Acts and sometimes called ('the coup within the coup'), was issued by dictator Artur da Costa e Silva, president at the time on December 13, 1968. It resulted in the forfeiture of mandates, interventions ordered by the President in municipalities and states and also in the suspension of any constitutional guarantees which eventually resulted in the institutionalization of the torture commonly used as a tool by the State.
Written by then Minister of Justice, Luís Antônio da Gama e Silva, it came as a response to earlier events such as a march of over fifty thousand people in Rio de Janeiro to protest against the murder of student Edson Luís de Lima Souto by a member of the Military Police of Rio de Janeiro, the March of the One Hundred Thousand, and the decision of the Chamber of Deputies denying authorization to prosecute Congressman Márcio Moreira Alves, which called Brazilians to boycott the celebrations of September 7 (Independence of Brazil). It also aimed to consolidate the ambitions of a group inside the military, known as "hardline", unwilling to give the power back to the civilians anytime soon.
Consequences
The immediate consequences of the AI-5 were: