Sign stealing itself is not against the rules, and has been a part of baseball since forever. It's something that can't really be prevented, like when you've go

Sign stealing itself is not against the rules, and has been a part of baseball since forever. It's something that can't really be prevented, like when you've got a runner off 2nd base and he can look right at the catcher when he's giving the signs. It's using electronics to steal signs that is against the rules. It's because electronics basically allow you to "perfectly" steal signs, and one of the biggest things in baseball is that the batter doesn't know what the pitcher is about to throw.