The Chief Justice in Nauru has rejected a government move to strike out Roland Kun's appeal to get his passport back.
The suspended opposition MP has been challenging the authorities' decision to cancel his travel document, which has left him unable to return to his family living in New Zealand.
He was pulled off a plane by authorities in June amid anti-government protests on the island, with the government alleging he was a national security risk.
At a court hearing on Monday the Chief Justice found Mr Kun should have directed his appeal to the justice minister, not the Secretary for Justice, and directed him to apply to have his notice of appeal formally amended.
The application is expected to be made on Tuesday.