I would go with MLB's exemption from federal antitrust law. For me, this was by far the most interesting topic of sports law and it presents a bevy of topics (so it ought to be an easy write). You would cover:
1) Federal Baseball v. National League;
2) The MLB reserve system;
3) Flood v. Kuhn (and the eventual Kurt Flood Act);
4) Piazza v. (don't remember off the top of my head but ought to be in your casebook);
5)Sherman Act;
6) NLRA; and there is probably more that is not coming to mind.
If you're more of a football guy you could probably write an interesting paper on the topic of what ramifications the N.O. Saints proposed decertification of the NFLPA would have on the upcoming CBA negotiations. I am not as familiar with this, but it is riddled with NLRA and Sherman Act issues.
If neither of these interest you, just watch Sports Center. Nearly everything you see in sports has legal issues (such as licensing rights, merchandising ect).
