The Papua New Guinea government says the refugee deported from Fiji could face criminal charges.
Loghman Sawari left Port Moresby on a false passport almost two weeks ago, but was taken by Fiji police on Friday as he traveled with his lawyer to meet immigration officials to apply for asylum.
The 21-year-old from Iran was detained on Manus Island by Australia at the age of 17.
Fiji's Attorney General Aiyaz Sayed-Khaiyum said he ordered Mr Sawari's deportation as he failed to apply for asylum in Fiji in a timely fashion.
He said as Mr Sawari was recognised as a refugee by PNG "Fiji merely returned him to his rightful place of residence."
The Guardian reports Mr Sawari was held inside the Port Moresby airport for more than five hours following his arrival on Friday, before being driven out of the international terminal by immigration officers.
PNG's immigration and foreign minister, Rimbink Pato told Fairfax "tendering false statements or documents as part of any application for a passport or travel document is a criminal offence in PNG. Breaches will be investigated and those breaking the law will be prosecuted."
Kurdish journalist and Manus Island detainee Behrouz Boochani said he had been notified that Mr Sawari was now in the custody of PNG police.