Right now the Mayor of Las Vegas wants to sue Ubisoft... because according to him the setting of the game isn't based on real buildings.
Ubisoft:
"In Tom Clancy's Rainbow Six Vegas, Team Rainbow is sent in to save Las Vegas from an escalating terrorist siege. The storyline of Rainbow Six Vegas is a work of fiction and should be held to the same standards as other forms of entertainment such as books and films. The game will be rated M for Mature by the ESRB and the marketing of the game will be consistent with its rating. Las Vegas is recognized as a world-class city just like Tokyo, Rome, London, Paris and New York thus making it a perfect location for works of fiction. In this case, Las Vegas provides our game developers with a captivating backdrop for an emotional storyline."