South Africa's main opposition party has filed papers with the Constitutional Court to challenge the government's decision to pull out of the International Criminal Court (ICC), it said on Monday.
South Africa will become the first country to quit the Hague-based court next year, after formally declaring its departure last week, saying ICC membership conflicted with its diplomatic immunity laws.
The opposition Democratic Alliance (DA) hopes the Constitutional Court, the final arbiter on constitutional issues, can intervene.
"The notice of withdrawal is in breach ... of the Constitution, as it was delivered without first securing a resolution of Parliament authorising South Africa’s withdrawal," the party said in a statement setting out its legal argument.
South Africa last year announced its intention to leave after the ICC criticised it for disregarding an order to arrest Sudanese President Omar Hassan al-Bashir, who is accused of genocide and war crimes, when he visited the country. Bashir denies the accusations.
The 124-member ICC is the first legal body with permanent global jurisdiction to prosecute genocide, crimes against humanity and war crimes but has secured only five substantive verdicts in 14 years, all of them on Africans, leading to criticism that it unfairly targets Africa.
Burundi's leader last week signed a decree to leave the ICC, and Kenya's parliament is considering following suit.
The head of the ICC's governing body, Senegal's justice minister Sidiki Kaba, said: "We regret these withdrawals."
"Clearly, the criticism brought against the International Criminal Court is that it is a vehicle of a two-speed justice, a selective justice, a justice of the white man," he said, but insisted "it was African countries themselves that chose to take their cases to the ICC."
South Africa's Business Day newspaper said in an editorial on Monday: "The intention to withdraw from the court undermines South Africa's reputation as a defender of human rights."