"Stealing signs is not a violation of Major League Baseball's (MLB) rulebook, depending on how the signs were stolen. According to the unwritten rules of baseball, stealing signs as they are given by the third base coach, or by a baserunner on second base watching the catcher's signals is acceptable, but a batter peeking in to see the signs is a violation; it is up to the defensive team to protect their signs so they are not stolen. The signs the catcher sends to the pitcher to relay the next pitch are considered more "sacred" than the signs a third base coach relays to the batter.

"At the December 1961 Winter Meetings, the National League banned the use of a "mechanical device" to steal signs. The use of electronic equipment is not specifically forbidden by MLB rules, though in 2001, Sandy Alderson while serving as executive vice president for baseball operations of MLB, issued a memorandum stating that teams cannot use electronic equipment to communicate with each other during games, especially for the purpose of stealing signs. Before the 2019 season, Rob Manfred, the commissioner of baseball, instituted specific prohibitions on where teams could position cameras and how instant replay officials can communicate with managers in an effort to reduce illicit sign stealing."