Tariq Ramadan is the world's most famous "moderate Muslim." He was slated to take a professorial job at the University of Notre Dame this year, until his visa was revoked by DHS. DHS hasn't explained why, and his case has become a cause celebre for the anti-anti-terror Left, but here is a French-language story (from the Swiss Le Temps, via [1] proche-orient.info, with thanks to Phil), that gives a hint as to why Ramadan may have been kept out of the U.S. Here is Phil's translation of the salient part:

According to the bill of indictment, Djamel Beghal, the preacher accused to have prepared a suicide mission against the American embassy in Paris, was preparing Tariq Ramadan's speeches.