South Africa's main opposition party says the government's decision to withdraw from the International Criminal Court is illegal and is asking the country's highest court to review the matter.

The Democratic Alliance party said Monday that the government acted unconstitutionally because it announced plans to withdraw from the human rights tribunal based in The Hague, Netherlands, without consulting the South African parliament. The party has filed an affidavit asking the Constitutional Court to hear its case.

Last week, South Africa notified the United Nations of its plans to pull out of the court after supporting its creation in 2002. The South African justice minister says a withdrawal bill will soon go to parliament, where the ruling party has a comfortable majority.