Former Nauru opposition MP Roland Kun has left Nauru and arrived in New Zealand after being issued with a New Zealand passport.
Mr Kun's Nauruan passport was cancelled amid accusations he had taken part in protests outside parliament - which he denies - and he had been unable to leave the country.
He applied for New Zealand citizenship in December last year in order to join his family in Wellington.
His lawyer, Claudia Geiringer, said his New Zealand passport was issued twelve days ago and sent to Nauru.
She said there were fears the Nauru government would attempt to arrest Mr Kun before he boarded the flight to New Zealand.
"Roland just presented himself at the airport yesterday. It was the day after the election and everybody was hungover," she said.
"He waited until the very last minute, slipped through Customs, got on the plane and he tells me that he thinks that at the point of departure the Nauru government did not know that he was on the plane."
Ms Geiringer said the case that they made for Mr Kun centred around the fact that he was the primary caregiver for his three young children.
"It really was a humanitarian tragedy that this man was being forced to stay in Nauru and couldn't be reunited with his family and that was at the core of our case," she said.
Under New Zealand law, the Minister of Internal Affairs is permitted to grant citizenship if he is satisfied that to do so would be in the public interest because of exceptional circumstances of a humanitarian or other nature.
"I'm so proud to be returning to my adopted country as a real Kiwi. After spending 12 months stranded in Nauru because of the actions of the government I just can't believe I'm finally going to see my beautiful family again," said Mr Kun in a statement.
"I'm extremely grateful for the assistance of my legal team and grateful for the consideration of Minister Dunne and the New Zealand Government on the matter of citizenship and the issuing of a passport," he said.