The Australian government's power to detain asylum seekers on the high seas and send them to other countries still needs to be determined, a High Court judge says.
Lawyers for 157 asylum seekers who were detained on an Australian Customs vessel at sea say the government's plan to send the group to India was not legal.
The asylum seekers set off from India on June 13 and their boat was intercepted in Australia's contiguous zone, off Christmas Island, on June 29.
They have since been sent to Nauru for processing.
High Court Justice Kenneth Hayne says the government's legal ability to detain people outside its migration zone and then release them in a foreign country has not yet been tested.
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"My concern is whether the government had power to take people from the contiguous zone to a place outside Australia," he said on Thursday.
"It may be that that is not the only legal issue."
Ron Merkel QC, for the asylum seekers, said the government's training of members of the group to pilot orange life boats during their detention indicated the government did not believe it could legally release them in India.
Commonwealth barrister Stephen Donaghue QC asked Justice Hayne for more time to negotiate with Mr Merkel to determine how the matter will go forward.
The matter will return to the court for further directions next Thursday.
