Brazil's Supreme Court banned corporate donations to election campaigns and political parties in a bid to avoid a repetition of the massive kickbacks scandal that has roiled the country.
The top court voted 8-3 to allow election donations from individuals but not from companies because it was "unconstitutional," concluded Chief Justice Ricardo Lewandowski.
Michael Mohallem, law professor at Fundacion Getulio Vargas in Rio de Janeiro, called it "one of the most important decisions in the recent history of the Supreme Court." He said it takes the influence of companies out of the political process.
In last year's presidential election, more than 80 percent of donations to candidates came from companies, according to O Globo newspaper.
Judge Luiz Fux, arguing with the majority, said that "economic power unlawfully dominates political power."
The court decision will apply starting with municipal elections next year, and for the 2018 presidential election.
Some of Brazil's most senior government officials and private sector executives, as well as a growing list of political figures, are among the dozens already tainted by the growing scandal at state-owned oil giant Petrobras.
The case -- which has seen growing calls for President Dilma Rousseff to resign -- involves an estimated $2.1 billion loss from inflated Petrobras contracts that went to a network of construction companies, which allegedly used the money to pay off politicians.