A refugee advocate says new laws restricting medical transfers off the island are putting refugee lives at risk.
Nauru rushed through regulations on Friday which will block medical referrals made by overseas doctors, including via online services.
It followed new laws in Australia granting doctors greater power to compel the transfer of sick refugees to Australia.
Lawyer George Newhouse from the National Justice Project said someone may die because of the laws and Nauru will be responsible.
"I'm incredibly concerned that the Nauruan government has passed laws which effectively hold extremely ill people prisoners on Nauru. For what purpose, I cannot fathom."
About 500 refugees remain on Nauru whose indefinite detention by Australia is Nauru's main source income.
Mr Newhouse said Nauru's government, which has not commented publicly on the new laws, was playing "politics with people's lives".
"If Nauru is going to play politics with people's lives and put people's lives at risk, then it's clear that they're not a suitable place for offshore detention and Australia should reconsider whether anyone should be housed on Nauru at all."