South Africa's Constitutional Court ruled on Friday that parliament had failed to hold President Jacob Zuma to account over a scandal related to state-funded upgrades to his home, and must launch proceedings that could remove him from office.
The ruling is the latest judicial setback for Zuma, who has faced widespread public demands to step down as president of Africa's most industrialized economy before an election in 2019.
While the ruling comes nowhere near starting an impeachment process against Zuma now, it gives parliament six months to make provision for the removal of a president.
It was not immediately clear what specific steps parliament would take, and whether any concrete action would be completed before the election, but analysts said the decision would add to the mounting pressure on him to step down.
The rand currency was almost 1 percent firmer on the last day trading day of the year.
Zuma, 75, is already in a weakened position after Deputy President Cyril Ramaphosa was narrowly elected leader of Zuma's ruling African National Congress (ANC) last week - although Zuma's faction still retains key positions in the party and he has already survived no-confidence votes.
"We conclude that the assembly did not hold the president to account ... The assembly must put in place a mechanism that could be used for the removal of the president from office," Judge Chris Jafta said, handing down the judgement, which was supported by a majority of the court, and shown on live television.
"Properly interpreted, Section 89 implicitly imposes an obligation on the assembly to make rules specially tailored for the removal of the president from office. By omitting to include such rules, the assembly has failed to fulfil this obligation."
The court ruled that parliament, where the ANC holds a commanding majority, needed to act within 180 days.
"The court is saying that there is no mechanism in place to implement the provision regarding impeachment ... They must make a provision within the rules for that to happen," said Lawson Naidoo, the executive secretary of the Council for the Advancement of the South African Constitution, an NGO.