Zuma had lodged a challenge at the court in Bloemfontein after a lower court decided in 2016 to reinstate charges that were previously dropped by prosecutors. The National Prosecuting Authority must now decide whether to pursue a prosecution.
“The reasons for discontinuing the prosecution given… do not bear scrutiny,” said Supreme Court judge Eric Leach, who read the ruling which Zuma could now contest on appeal to the Constitutional Court, South Africa’s highest.
The opposition Democratic Alliance party had sought in 12 court appearances since 2009 to reactivate 783 charges regarding controversial post-apartheid military contracts that have dogged Zuma for much of his time in government.
The president, who is accused of corruption, fraud, money-laundering and racketeering, has always insisted he is innocent. Just back in South Africa from a visit to Zambia, he has yet to comment on the judgement.
Zuma and other government officials were accused of taking kickbacks from the $5 billion (4.2 billion euros) purchase of fighter jets, patrol boats and other arms manufactured by five European firms, including British military equipment maker BAE Systems and French company Thales.
In 2005 Zuma’s former financial adviser Schabir Shaik was convicted for facilitating bribes in exchange for military hardware contracts and sentenced to 15 years in prison. He was later released on medical parole.
‘Much more vulnerable’
Charges were first brought against Zuma in 2005 but dropped by prosecutors in 2009 before their reinstatement some seven years later.
Constitutional expert Lawson Naidoo described the Supreme Court judgement as a “significant blow” for Zuma.
“He may petition the Constitutional Court but it appears that he has no legal basis for that after his legal team conceded that the decision to drop the charges was indeed irrational,” he said.
The Supreme Court heard arguments last month against reinstating the charges, but in an unexpected twist Zuma’s lawyer Kemp J Kemp agreed that the decision by prosecutors to drop them in the first place was irrational.
The Supreme Court ruling could intensify calls for Zuma to resign and cast a shadow over a conference of his ruling African National Congress (ANC) party, due to be held in mid-December, which will elect his successor.
The case is the latest in a string of political and legal scandals that have haunted the president but failed to shake his grip on power.
In 2016 Zuma was ordered to repay $24 million (22 million euros) to the public purse for upgrades to his personal residence that judges said showed he had disrespected the constitution.
“He’s going to try to fight back, but I think it will empower some within the ANC to extend a hand to him to say maybe this is a deal we can give you to get out,” said political analyst Ralph Mathekga ahead of the ruling. “He’s going to become much more vulnerable.”