On April 15, 2011, the U.S. Attorney's Office for the Southern District of New York seized and shut down Pokerstars and several of its competitors' sites, alleging that the sites were violating federal bank fraud and money laundering laws.
The PokerStars website is available in the United States, but only players in a handful of states can access the real money games listed there. This isn't because PokerStars doesn't want you at the tables. The poker site is active in almost all the US states that have legalized online poker.