There are a number of sources for these rules, but they all ultimately are sanctioned by the Office of the Commissioner of Baseball.
Other examples include: The Official Professional Baseball Rules Book is organized into the following sections: The below sections enumerate the numbered Major League Rules, both before and after Major League Baseball reorganized the minor leagues in advance of the 2021 season, as multiple rules were changed at that time.
With the elimination of one-game playoffs in 2022, the tiebreaker rules were significantly modified, since all ties are now resolved by formula.
[1] The Major League Rules begin with a note stating that whenever a provision of any of its rules conflicts with a provision in the Basic Agreement (collective bargaining agreement) negotiated with the Major League Baseball Players Association, the provision in the Basic Agreement "shall in all respects control".
There are then Attachments to the Rules (numbers refer back to Rule # above): Source:[4] At the top of page 1, a bolded, fully capitalized statement indicates that where the rules conflict with the currently effective basic agreement with the Major League Baseball Players Association, the basic agreement controls.