Can Congress send Lula back to prison?

Earlier this month, Brazil’s Supreme Court concluded a trial on the possibility of executing prison sentences after a single appeal. The vote came right down to the wire, with Chief Justice Dias Toffoli settling the ruling at a 6-to-5 majority, establishing that defendants may only go to jail after exhausting all of their appeals routes.

This represented a change to the court’s precedents and allowed the release of several thousands of felons still awaiting high court appeals—among them former President Luiz Inácio Lula da Silva, who remains the most divisive figure in modern-day Brazilian politics.

The political furor was such that as soon as the outcome of the Supreme Court trial became clear, members of Brazil’s Congress went about debating a constitutional amendment to legislate for the possibility of allowing defendants to go to jail after a single failed appeal. However, there is much doubt about whether such a change is even possible.

In Article 5, Item 57 of the Brazilian Constitution, it says that “no one shall be considered guilty before the issuing of a final and unappealable penal sentence.” And as this is regarded as an “entrenched clause” in the Constitution, jurists are split over whether...