The government's move came during a High Court hearing held a day after Australia's immigration minister confirmed another boatload of asylum seekers had been intercepted by Australian border patrol and transferred to Sri Lankan authorities at sea.
Refugee advocates have criticised the move, saying the asylum seekers will face persecution in Sri Lanka.
Lawyers for asylum seekers on board a second boat that has been intercepted went to the High Court to stop the 153 people on that vessel from also being returned to Sri Lanka. They are currently on board an Australian customs vessel.
Government lawyers said no asylum seekers would be transferred without 72 hours' written notice.