A legal attempt to overturn Schapelle Corby's clemency has fallen at the first hurdle, with a judge telling the hard-line anti-drug group which brought the case that its argument was not valid.

Judge Yodi Martono Wahyunadi of the Jakarta administrative court today rejected the case by brought by anti-drugs group Granat, saying the president's grant of clemency was valid.

In Indonesian law, the president, Susilo Bambang Yudhoyono, can grant clemency to any prisoner. In May, he reduced the Australian drug-smuggler's sentence by five years to 15 years, making her eligible for parole.

The decision prompted an angry backlash from many people in Indonesia, who said it sent the wrong signal and suggested that the country was soft on drugs.

Part of the backlash was a legal case brought by anti-drugs body Granat, and argued by a high profile enemy of the president's, Yusril Ihza Mahendra, a former justice minister who has won a number of cases against Mr Yudhoyono's decisions in the past.

However, in this case, the judge said there was no administrative dispute because the president was lawfully exercising his prerogative rights in accordance with Indonesia's constitution.

Granat said after the case that the judge had not taken into account their arguments, and that they would appeal.

The argument is complex and centres on whether the president was acting as the president when he made the grant of clemency. The lawyers have claimed that, because he gave no explanation of his decision, that it was not a proper exercise of his prerogative.

The backlash against the Corby decision has spooked the president, who is already seen in Indonesia as being too close to foreign powers.

It makes it more difficult for him to spare the lives of Australia's two death row prisoners, Bali Nine smugglers Andrew Chan and Myuran Sukumaran, whose clemency appeals are now in train.

The man who brought the case, Henry Yosodiningrat, head of Granat, said he would "definitely" appeal.

"Of course we're disappointed but we have to challenge it with respect through legal procedures," he said.

-The Age