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Pretty hard, but not impossible. We have a lot of ISP, so there are a lot of pieces to the puzzle. Keep in mind, though, that many American ISPs have a history of doing what the government asks, even when it is illegal. I read an interesting blog on this topic, where the author basically posits that the more ISPs there are, the harder it is to completely shut down. http://www.renesys.com/blog/2012/11/could-it-happen-in-your-countr.shtml