<P> One of these MLB Rules (5.05 (a) (9)) governs when fair fly balls are deflected into the stands by a fielder: for example, a fair fly ball deflected out of play by a fielder from a point within 250 feet of home plate is considered a double . This applied in an unusual play August 3, 2007 when Melky Cabrera of the New York Yankees hit a ball that ricocheted off Kansas City Royals pitcher Ryan Braun's foot and bounced into the stands in foul territory . </P> <P> When two bases are awarded by either ground rules or the automatic rule, any baserunners ahead of the batter are entitled to advance two bases from their positions at the time of pitch . Only in the case of interference is the umpire vested with discretion to award more bases . The ground rule or automatic double frequently results in a runner at first base who appears to have been able to score on the batted ball nevertheless being returned to third base when the ball goes out of play . </P> <P> In the early years of baseball, all batted balls that cleared the fence after a bounce in fair territory or on a fly were counted as home runs . The rule was changed by the American League prior to the 1930 season and subsequently by the National League on December 12, 1930 . Notably, the pre-1930 rule includes most of Babe Ruth's career . Early baseball statistics do not differentiate between home runs that cleared the fence on a bounce compared to those that did not . However, most baseball historians believe that Ruth likely missed out on more home runs that did not count due to other differences in the rules in place during his career compared to the number of home runs he likely hit off bounces . </P>

When did the ground rule double go into effect