BRASILIA (Reuters) - In allowing Luiz Inacio Lula da Silva to walk out of jail last week, Brazil’s Supreme Court has blown open a legal labyrinth that could see the leftist former president return to prison just as easily as run for election again.

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The second chamber of the Supreme Court will soon hear an appeal from Lula’s defense team that Sergio Moro, the judge in the wide-ranging “Car Wash” corruption probe who secured Lula’s conviction and who is now justice minister in far-right President Jair Bolsonaro’s cabinet, did not act impartially.

The Supreme Court on Friday ruled that a person can only be imprisoned once all appropriate avenues of appeal are exhausted, so-called “res judicata”, which overturned the court’s opinion three years ago that convicted criminals face mandatory imprisonment if they lose their first appeal.

Seventy-four year old Lula had been imprisoned for 19 months on corruption convictions carrying a nearly nine-year sentence. He is also facing several other corruption charges.

If the Supreme Court’s second chamber annuls Lula’s conviction, he will once again be eligible to run for office, potentially opening the way for him to stand as the Workers’ Party (PT) candidate in the 2022 presidential election.

On the other hand, if he loses an appeal relating to one of his other charges known as the “Atibaia” case, Lula could return to prison. Following last week’s Supreme Court ruling, lawmakers have advocated speeding up a constitutional amendment reinstating automatic jail time for convicts who lose their first appeal.

Both the Lower house and Senate are currently analyzing constitutional amendments on this subject. Because they take longer to go through the legislative process than ordinary bills, nothing is likely to happen until next year.

The case against Moro and his alleged political bias in Lula’s conviction had been stalled since December last year, when justices Edson Fachin and Carmen Lucia took a stand against it and justice Gilmar Mendes requested a review of the case.

“Annulling (Lula’s) conviction, if that’s what eventually transpires as a result of (Moro’s role), will lead to a new trial. That could happen,” justice Mendes said in an exclusive interview with Reuters in August.

“It is important to do this analysis in a detached way. The media became very oppressive. The right verdict is not just a guilty verdict. This is not correct. We have to recognize that we owe Lula a fair trial,” Mendes said at the time.