South Africa's top court on Friday blocked the release from jail of Polish immigrant Janusz Walus who shot dead anti-apartheid hero Chris Hani in 1993.
Walus, 64, has served 24 years of a life sentence for the murder, which took South Africa to the brink of race war as negotiations to end apartheid entered their final phase.
The Supreme Court upheld an appeal by the government to overturn last year's High Court decision to free Walus on parole.
Walus killed Hani, a popular leader of the Communist Party, one year before South Africa's first multi-racial elections.
His accomplice, Clive Derby-Lewis, who supplied the gun, was released in 2015 on medical parole after serving 22 years in jail. He died of lung cancer last year, aged 80.
Walus immigrated to South Africa from then-communist Poland in 1981.
One of South Africa's most notorious apartheid murderers, Eugene de Kock, was granted parole in January 2015 after 20 years in jail.