That's called extortion and it's illegal. This is not extortion, its an informal agreement willingly entered by 2 parties. If the Cubs were employing Sveum and keeping him from accepting a position with the Red Sox, that would be extortion. If the Red Sox say no, the Cubs can't make things more difficult for the Red Sox other than keep persuing Sveum, which they have every right to do. If the Red Sox say ok and still demand McNutt, the Cubs can't do anything either. But they can discuss a scenario that is mutually beneficial for each of them and keep it between themselves no official agreement.