It wouldn't be legal, unless they could somehow link Tony to a terrorist organization. They were going down that route toward the end of the show, which was why Tony started ratting off Christopher's Muslim friends to them.

"...the successful annihilation of organized crime's subculture in America would rock the 'legitimate' world's foundation, which would ultimately force fundamental social changes and redistributions of wealth and power in this country. Meyer Lansky's dream was to bond the two worlds together so that one could not survive without the other." - Dan E. Moldea