South Africa's Supreme Court of Appeal has dismissed a government appeal and ruled that its failure to arrest Sudanese President Omar Al Bashir was unlawful.

"The decision by the South African government not the arrest Al-Bashir was inconsistent with South African law. Therefore the application is dismissed," Judge Carole Lewis said on Tuesday.

The South African government had wanted the initial North Gauteng High Court ruling, that it should have arrested the Sudanese leader when he was in the country, overturned.

President Bashir was in South Africa to attend an African Union Summit in June last year. The Southern Africa Litigation Centre (SALC) filed an application for his arrest at the Pretoria court, but the government allowed him to fly out of the country in contravention of a court order.

As a signatory to the Rome Statute, and the ICC Act of 2002, South Africa was obligated to detain the Sudan president and ease his extradition to The Hague.

Last month, the government argued in the appellate court that as a sitting head of state, that Sudanese leader enjoys diplomatic immunity.

Diplomatic immunity

South Africa's government lawyer Jeremy Gauntlett told the court that there was no obligation on South Africa to arrest him, quoting a notice gazetted a week before Mr Bashir arrived stating that all delegates at the summit would enjoy diplomatic immunity.

In his submission for the SALC, lawyer Wim Trengove said the question on whether President Bashir should have been arrested while in in the country did not touch on whether he would have been prosecuted in the country’s courts but rather that he should have been handed over to the ICC for prosecution.

The Sudanese leader is wanted by the International Criminal Court (ICC) for war crimes and crimes against humanity for atrocities committed in the Darfur conflict.

The ruling means that Bashir and others facing global arrest warrants for crimes against humanity would be arrested if they set foot in South Africa. In addition, the High Court had said previously that the National Prosecuting Authority should consider whether to take action against the government for letting Bashir leave the country.

In the aftermath of the initial court ruling, the governing African National Congress party said South Africa should withdraw from the ICC, which African states have accused of bias against the continent.

Judges at the ICC have also asked South African authorities to explain why they failed to arrest Bashir.

Additional reporting by Reuters.