It's been more than a year since Chinese rights lawyer Gao Zhisheng disappeared into police custody. Chinese security officials took Gao from his home in Shaanxi Province on February 4, 2009.

Now Gao's international legal team and the NGO Freedom Now are petitioning the United Nations to declare Gao’s detention a violation of international law.

The petition, filed on Tuesday to the U.N. Working Group on Arbitrary Detention, says the Chinese regime has also violated its own laws. While detaining Gao for more than a year, Chinese authorities have not charged him with a crime and have denied him contact with the outside world.

Although considered one of China’s most promising lawyers, Gao became a target of the Chinese regime. In 2006 he was found guilty of so-called “inciting subversion.” It came after Gao wrote open letters to Chinese Communist Party leadership asking them to stop persecuting members of the Falun Gong spiritual group.

On Wednesday, independent U.N. expert on torture Manfred Nowak told the Associated Press that he is “very concerned” about Gao’s current situation.

In February 2009, Gao released a detailed account of how he was kidnapped and tortured in September 2007 after sending an open letter to the U.S. Congress on the Chinese regime's human rights violations.