Australia's Human Rights Law Centre says the opening up of Nauru's asylum seeker detention centres is welcome but fundamental problems remain.
The Nauru government says asylum seekers are free to come and go from the detention centre 24 hours a day from today.
The law centre's director of legal advocacy Daniel Webb says serious constitutional questions remain about Australia's involvement in offshore detention and the validity of the laws attempting to authorise it.
He says the asylum seekers need the real solution of being settled in a safe place where they can rebuild their lives.
Mr Webb says the transition to an open centre comes two days before the High Court in Canberra examines Australia's role in offshore detention on Nauru.
The case involves a woman from Bangladesh facing imminent return to Nauru after being brought to Australia for urgent medical care.
It is the lead case linked to a series of challenges being run on behalf of more than 200 people in similar situations.