Beijing lawyer Li Jin said that Guo Yushan, founder of the nongovernmental think tank Transition Institute, was released yesterday, but she could not provide details on why he was freed or whether the release had anything to do with Xi's upcoming meeting with President Barack Obama.
Guo was detained last October and charged in January with operating an illegal business. The charge remains, but can expire one year after his release.
Chen eventually made it to New York, after Hillary Rodham Clinton, then the US secretary of state, negotiated for him to attend school in the United States.
Guo's Transition Institute conducted research on China's social and economic issues, but Beijing authorities, citing lack of proper registration, shut down the organization in 2013.
Guo was detained at a time when Hong Kong protesters were demanding universal suffrage in elections for the semiautonomous city's top official.