The US government won't grant the necessary permission for Cuba to play in the World Baseball Classic. Cuba requires a permit to play in Puerto Rico.
http://mlb.mlb.com/NASApp/mlb/news/a...=.jsp&c_id=mlb
The US government is playing petty politics here. Cuba is a serious baseball contender. This move tarnishes the image of the tournament.
While Cuba's politics leave much to be desired, Castro has been a source of embarassment after managing to survive 10 different U.S. Presidents.