Blind activist Chen Guangcheng has challenged China's central government to prove it didn't order his illegal house arrest.
Chen spent two years under house arrest after serving a four-year jail sentence on charges related to his work exposing forced sterilizations and abortions under China's population control policy.
No legal explanation for his detention was announced by local authorities in his home province of Shandong.
Chen spent six days in the U.S. Embassy after escaping in late April before he was taken to a Beijing hospital under a deal between the Chinese and the U.S. governments.
Chen said on May 9 that he was told by U.S. officials that paperwork necessary for him to study in New York has been completed, but he is still waiting for his passport to be returned by Chinese officials.
Based on reporting by AFP and Reuters