Anyone with more than a passing familiarity with baseball knows that there’s at least one important rule difference between the American League and the National League: in the AL, the pitcher never bats, and is instead represented by the Designated Hitter, a player who never takes the field. Interestingly, the rule that governs this is 6.10, which begins by stating “Any League may elect to use the Designated Hitter Rule.” Apparently the NL has simply elected not to use it. More interestingly, there are a few minor official rules that specifically apply to only NL or AL teams:

  • 1.16(b) - All NL players have to wear a double ear-flap helmet while at bat. According to 1.16(c), almost all other players are simply required to wear one with at least one ear flap. (Aside: Rule 1.16(c) actually grandfathers in players who chose in 1982 to not wear a helmet with ear flaps. Tim Raines was the last player to wear a helmet without ear flaps. He retired after the 2002 season. Julio Franco is the only still-active player who would qualify under this rule. Unfortunately, he chose to wear one-flap helmets, even before they were required.)
  • 4.10(a) - The National League can adopt a rule changing one or both double-header games to be seven innings long. The AL does not have that right. As far as I know, such a rule has never been adopted.
  • 4.12(a)(7), 4.12(a)(8), and 4.12(a)(9) - The NL can adopt a rule making games that have been stopped before regulation (for instance, because of rain) a "suspended game" instead of "no game".
  • 6.02(d) - The NL had to follow this experimental rule in 2006, essentially saying that the batter could not leave the batter's box unless either team was making a substitution or calling a conference. I have no idea if they're planning to make it permanent.
  • 10.23(b) - In the AL, the league pitching champion must have pitched at least as many innings as the number of games each team played that season (162 this year). In the NL, the champion only needed to have pitched 80% that many innings (129.6). As far as I can tell, this rule rarely, if ever, actually matters. The top pitchers in both leagues usually pitch at least 190 innings a year.