Chen Tianben, a legal professor with the Chinese People's Public Security University, told the Global Times that police could only arrest Xu if he was a threat to public security, otherwise their actions would constitute a breach of the law.

It was not the first time a petitioner has been sent to a hospital for having a "mental illness."

Xu Lindong a petitioner from Henan Province, was taken away from Beijing in October 2003 and sent to an asylum in Zhumadian, Henan, where he was locked away for six and a half years. In April 2010 he was rescued and received compensation of 300,000 yuan (US$44,000).

A commentary carried by the People's Daily on Thursday called for a mental health law and transparency when admitting mentally ill patients to hospitals. Xu's case indicates that the relevant government departments have to improve their work and also highlights the lack of a mental health law, the opinion piece said.

There is neither any clear description on circumstances for the compulsory admission of a mentally ill patient into hospital, nor any standard procedure, it said.

Mentally ill patients are citizens who are protected by the law, and admitting and treating them has to be conducted under strict procedures, not in a secret environment away from the public, media and family members, said the People's Daily commentary.

Health Minister Chen Zhu said in March that the Mental Health Law is expected to be delivered within the year.