The US envoy to the WTO urged China to explain why its “Great Firewall” blocks many American companies from doing business over the internet in China, Reuters reported. Reuters obtained a copy of a letter US Ambassador to the WTO Michael Punke. Punke told to his Chinese counterpart that he wants clarifications on the guidelines for blocking foreign websites and how they are made public. Punke did not threaten legal action or challenge China’s right to restrict internet activity in the first place, but did say that the lack of transparency violates WTO laws that China has agreed to as a member of the organization. China bans social media sites Facebook, Twitter and YouTube in addition to some foreign news publications to limit dissenting views, but some American online services claim that they are firewalled despite having no political content, making the blockages a form of trade protectionism. Websites in China are generally blocked with little explanation.