Residents take part in a demonstration in support of Brazilian President Dilma Rousseff government and former President Luiz Inacio Lula da Silva, in Sao Paulo, Brazil, on March 18, 2016. Former Brazilian President Luiz Inacio Lula da Silva could take up the post of chief of staff in the cabinet of President Dilma Rousseff following a judicial decision in his favor, official sources said on Friday. [Photo/Xinhua]

RIO DE JANEIRO -- A Brazilian Supreme Court judge on Friday suspended former President Luiz Inacio Lula da Silva's newly appointed cabinet post and returned the corruption case against him to criminal court.

The preliminary injunction holds until the full court can rule on the legality of President Dilma Rousseff's decision to appoint Lula, her predecessor and mentor, as her chief of staff.

The decision by Justice Gilmar Mendes is set to stir up more tensions in the country's volatile political realm, which has witnessed waves of pro- and anti-government protests.

The former president is embroiled in a corruption investigation, but he denies any wrongdoing. Should he become a cabinet minister, he would have immunity from prosecution in criminal court, and can only be tried before the Supreme Court.

Sending the corruption case against Lula back to judge Sergio Moro, who leads the highly controversial investigation against state oil company Petrobras, Mendes said the fact that Lula's appointment had the effect of removing him from Moro's jurisdiction "could amount to an act of fraud against the constitution."

The Brazilian government can appeal the decision.