Moreover, unless policymakers are willing to challenge human rights violations through trade dispute mechanisms, we won't know if trade agreements really work to advance human rights. For example, both the U.S. and the E.U. are deeply concerned about Internet censorship and filtering, particularly in China. China's web filtering and firewall act as trade barriers, and they aren't applied in a uniform and impartial way. In 2010, senior European Commission leaders threatened a trade dispute. And in late 2011 the U.S. government sent a letter to the Chinese government asking it to explain why some foreign sites (such as Google) were inaccessible in China, who decides if and when a foreign website should be blocked and if China has an appeal procedure for such blockage. Although China was required to respond under World Trade Organization rules, the U.S. government never received a formal reply. Neither the U.S. nor the E.U. moved forward. Hence, we don't know if we can effectively challenge censorship (a violation of human rights) as a trade barrier.