No rule in all of sports has generated as much legal scholarship as baseball’s Infield Fly Rule. Interestingly, however, no one has explained or defended that rule on its own terms as an internal part of the rules and institutional structure of baseball as a game. This paper takes on that issue, explaining both why baseball should have the Infield Fly Rule and why a similar rule is not necessary or appropriate in seemingly comparable, but actually quite different, baseball situations. The answer lies in the dramatic cost-benefit disparities present in the infield fly and absent in most other baseball game situations.

The infield fly is defined by three relevant features: 1) it contains an extreme disparity of costs and benefits inherent in that play that overwhelmingly favors one team and disfavors the other team; 2) the favored team has total control over the play and the other side is powerless to stop or counter the play; and 3) the cost-benefit disparity arises because one team has intentionally failed (or declined) to do what tordinary rules and strategies expect it to do and the extreme cost-benefit disparity incentivizes that negative behavior every time the play arises. When all three features are present on a play, a unique, situation-specific limiting rule becomes necessary; such a rule restricts one team’s opportunities to create or take advantage of a dramatic cost-benefit imbalance, instead imposing a set outcome on the play, one that levels the playing field. The Infield Fly Rule is baseball’s prime example of this type of limiting rule. By contrast, no other baseball situation shares all three defining features, particularly in having a cost-benefit disparity so strongly tilted toward one side. The cost-benefit balance in these other game situations is more even; these other situations can and should be left to ordinary rules and strategies.