As much as it pains Sir Alex and co., Manchester United is going to have to let Ronaldo go unless they want to risk long term damage to their club and reputation. As EPL Talk says, it’s really obvious he wants to go and when a player of his calibre wants to move, he’ll get his way. It’s the way of the soccer world right now.
Sure United could refuse any offers, but then Ronaldo could pout or get injured thus slashing his value enormously. United could also conceivably hold on to him, but bolt his rear to the bench. That would damage the club’s reputation among players and agents who wouldn’t want their careers slashed and burned by the Scotsman.
You hope that someone at United has the ability to veto Ferguson if he does have this “nuclear” option in mind. Someone has to prevent him from cutting off his own bulbous nose in spite of his very purple face.