I don't think you can get a warrant to block a website.
They must be able to because the government can shut down child pron sites. Since I really do not know able the sites listed it is hard to say what they were shut down for. If the sites were used by terrorists to communicate with each other or to recruit new members it seems the government can and should shut them down. If they are just factual sites about terrorists then it might be a problem with censorship. That is a really fine line.