AFP/ Jakarta

Lawyers fighting to save the lives of two Australian drug smugglers on death row returned to court on Monday to challenge the Indonesian president's rejection of their pleas for mercy.

They presented an expert defence in an attempt to show that judges have the right to rule on the clemency issue, despite an earlier ruling to the contrary.

Myuran Sukumaran and Andrew Chan, the ringleaders of the so-called "Bali Nine" drug trafficking gang, were sentenced to death in 2006 for trying to smuggle heroin out of Indonesia.

Their appeals for clemency, typically the final chance to avoid the firing squad, were recently rejected by Indonesian President Joko Widodo, who has taken a hard line against traffickers.

The men, in their early 30s, were moved this month from jail on Bali to Nusakambangan prison island off Java, where they will be executed along with several other foreign drug convicts.

In the latest attempt to save the men from the firing squad, their legal team has challenged Widodo's decision to reject the clemency pleas, arguing that he failed to assess their rehabilitation or give reasons for his decision.

The Jakarta State Administrative Court dismissed the bid last month, saying it did not have the right to rule on the matter because granting clemency is the president's prerogative. The Australians' lawyers are now appealing that decision.

On Monday Otong Rosadi, a law lecturer presented as an expert witness, argued the judges did have the right to rule on the president's decision after a constitutional amendment around 15 years ago, which states that public policies can be challenged in court.

"After that amendment, the president's prerogative rights were no longer absolute," he said.

Rosadi, from Ekasakti University on Indonesia's Sumatra island, also said that "the right place to contest that presidential decision is the Administrative Court".

But he added that there had been no previous court cases relating to the president's decision to reject a clemency plea.

The Australians are expected to be executed at the same time as eight other drug convicts, including citizens from France, Brazil, the Philippines, Ghana and Nigeria.

Jakarta originally said the executions would take place in February. But following an international outcry it decided to postpone them until all legal appeals had been completed.

A Frenchman and a Ghanaian also have appeals pending. Last week, the Supreme Court rejected a Filipina's appeal and she is expected to be transferred soon to Nusakambangan.