From Ken Davidoff:

Jason Giambi probably had the law on his side. But he lacked the desire to engage in an imbroglio with Major League Baseball, so the Yankees designated hitter officially capitulated Thursday, agreeing to become the first known active player to speak with baseball steroids investigator George Mitchell. ...

The Yankees, by virtue of this arrangement, will not attempt to void the remainder of Giambi's contract.

Via Steve.