If you do not look at the weekly postings on the Becker-Posner Blog, you are missing some great writings from two notable scholars. At the end of Posner's posting, he has a "by-the-way" about steroids and athletics, which has already provoked some interesting discussions in the comments section of their blog.
Oddly, one of the strongest cases for prohibiting drugs is the use of steroids by athletes. The reason is the arms-race character of such use, or in economic terms the existence of an externality. Ordinarily if a person uses a drug that injures his health, he bears the full costs, or at least most of the costs, of the injury. But if an athlete uses steroids to increase his competitive performance, he imposes a cost on his competitors, which in turn may induce them to follow suit and use steroids themselves, provided the expected costs, including health costs, are lower than the expected benefits of being able to compete more effectively. There is no offsetting social benefit from an across-the-board increase in athletes’ strength. Football games are no more exciting when linesmen weigh 500 pounds than when they weigh 200 pounds; and baseball would be totally unmanageable if every player could hit every other pitch 1000 feet.
Posner is correct that taking steroids is like a prisoners' dilemma game, but I expect it is not a zero- or negative-sum game. Fans love bigger and stronger performances, and it is quite likely that the renaissance of baseball has been due, in part, to the rising slugging average that in turn was due, in part, to steroid use. If so, then if baseball's ban on steroids is effective, fan interest in baseball might tend to drop off a bit over the next few years.