Disappointed, yes. Surprised? Hardly. Nick Diaz loves him some weed, and the Nevada State Athletic Commission has busted him for it again. In 2007, his amazing gogoplata win over Takanori Gomi in Las Vegas was bumped down to a "No-Contest" after Diaz tested positive for marijuana. Later that year, Diaz told Sherdog that he considered smoking pot to be "good for mixed martial artists." Yeah, this isn't a guy who's going to lay off the medicine pipe in training camp. Diaz is one of the best fighters on the planet. He's also one of the least tractable, which is why so many people love him and so many others hate him.
What's disappointing—and this is probably what White means by that statement (which I just now received from the UFC by email)—is that it's unlikely we'll be seeing Diaz in the UFC again for a long time. Or ever, if his comments after his controversial loss to Carlos Condit last weekend are any indication.