This is an odd case brought under antitrust law. The plaintiff is a former umpire who was fired for racist and offensive activities. The case just survived a motion to dismiss, in which Minor League Baseball argued that the antitrust exemption applied to the minor leagues. The court said that the exemption did not apply, and that the case could proceed to the discovery phase. In other posts, I have discussed Major League Baseball's antitrust exemption (Why does Major League Baseball have an antitrust exemption?, More on the antitrust exemption in baseball).
I find it hard to believe that the plaintiff will make it very far in this case. He contends that the minor leagues run an illegal monopoly, but even if the defendants have a monopoly over umpiring in baseball, there is no monopolizing conduct. To be an illegal monopoly, you need to have monopolizing conduct. So, basically, it is an interesting case, but one the plaintiff is extraordinarily unlikely to win.