Lawyers specialising in international law say moves against an opposition MP in Nauru go against international human rights law.
The Nauru government has cancelled Roland Kun's passport over security fears, preventing him from returning to his family living in New Zealand.
A council member of the Australian/New Zealand Society of International Law Kim Rubenstein says the moves against Mr Kun are an assault on his rights to free speech, movement and family life as laid down in an international covenant.
"Article 19 of the International Covenant on Civil and Political Rights protects freedom of expression, the cancellation of his passport in Nauru has an impact on his freedom of movement and Article 12 affirms the right to liberty of movement and the capacity to be free to leave any country including your own country."
Professor Rubenstein says she is preparing a letter for members to sign which will go to the Foreign Ministers of Australia and New Zealand highlighting their concerns.
Nauru signed the International Covenant on Civil and Political Rights in 2001.