The unanimous decision by the court's 11 judges rejected the argument often advanced by Bolsonaro and his far-right backers that Brazil's constitution establishes the military as a "moderating power" that can intervene in government in times of crisis.

"It is urgent to put a stop to dangerous interpretations that distort the constitution and threaten the democratic rule of law," Luiz Fux, the lead judge on the case, wrote in his ruling.

Ex-army captain Bolsonaro, who led Brazil from 2019 to 2022, has repeatedly evoked the supposed constitutionality of a military intervention in politics.

He is now under investigation over allegations he and top advisers, including high-ranking military officers, orchestrated what federal police call a "coup attempt" to keep him in power after Brazil's 2022 elections, which he lost to veteran leftist Luiz Inacio Lula da Silva.

Investigators say Bolsonaro, an avowed admirer of the military dictatorship that ruled Brazil from 1964 to 1985, edited a draft decree that would have declared a state of emergency and called new elections.

Bolsonaro, who attacked Brazil's voting system as fraud-prone throughout the campaign, denies wrongdoing, saying he is the victim of political persecution.

Bolsonaro and his backers often cite Article 142 of Brazil's 1988 constitution as allowing a military intervention in case of a breakdown in government institutions.

The center-left Democratic Labor Party (PDT) asked the Supreme Court to rule on that interpretation.

The high court roundly rejected it.

"The same constitution that says 'all power emanates from the people' in its first article cannot be read as authorizing a 'military intervention,'" wrote Fux.

The ruling comes on the heels of the 60th anniversary of the March 31, 1964, coup that installed the dictatorship.

National debate around the anniversary drew new relevance after Bolsonaro's defeat and riots by his supporters, who stormed the seat of government in Brasilia on January 8, 2023, alleging the elections were stolen and urging the military to intervene.