On Monday, lawyers won a 24-hour injunction after arguing that the government had not processed the migrants' claims for asylum in accordance with the law.
Canberra has already faced criticism after a boatload of asylum seekers were repatriated to Sri Lanka, where it is claimed they face ill treatment by the authorities.
Over the weekend, Australia's customs agency intercepted the boat carrying the latest migrants, 37 of whom are children, and has since held the people at sea. Solicitor George Newhouse told the Australian Broadcasting Corporation that the country would put the asylum seekers at risk by returning them to a land where they faced imprisonment and torture.
"The minister can't simply intercept them in the night and 'disappear' them," Newhouse said on Monday. He added that the migrants "claim that they are fleeing persecution and that they are at risk of death, torture or significant harm."
On Sunday, Australia returned 41 Sri Lankans intercepted by the border patrol in late June, according to a statement. One official said that four of the asylum seekers on board were Tamils, but denied that any were in danger of persecution.
The minority is said to face persecution after the war between the government and the separatist Tamil Tigers. The Tamil Refugee Council claims Sri Lanka's intelligence services previously tortured 11 of those on board. Sri Lanka announced that those returned would face two years of "rigorous imprisonment."
In the past three months, three Tamil asylum seekers on temporary visas in Australia have set themselves on fire at the prospect of being sent back to Sri Lanka. Two died.
Newhouse is also representing the families of eight Iranian and Iraqi migrants who drowned trying to reach Australia on a boat crowded with dozens of people, alleging that the government did not do enough to rescue them.
Under right-wing Prime Minister Tony Abbott, Australia turns back migrants at sea, generally to Indonesia, where asylum seekers from several countries pay people smugglers to get them to Australia aboard boats that are often unseaworthy. Officials deny that this violates international obligations, and the government won a recent High Court case allowing it to process migrants in Papua New Guinea instead of on its own turf. Still, Australia faces growing criticism over its treatment of migrants.
In 2013, Australia received 16,000 asylum seeker applications, just under 0.5 percent of the 3.6 million lodged worldwide, according to UN figures. Abbott won last September partly because of his tough stance on asylum seekers. Though his popularity has since plummeted, over 70 percent of Australians support the government's border policy, including sending boats back when safe to do so, according to a recent poll by the Lowy Institute think tank.
Australian Immigration Minister Scott Morrison plans to visit Colombo this week to attend a handover ceremony for two patrol boats his country will give the Sri Lankan Navy.
mkg/rc (Reuters, AFP, dpa, AP)