There is no law preventing a league from fixing its own contest. The two closest federal laws on the books are these:
The "Quiz Show" law which was passed after it was revealed that television networks had been fixing the outcome of nationally televised game shows including Twenty-One and the $64,000 Challenge. The law reads: "(a) Influencing, prearranging, or predetermining outcome
It shall be unlawful for any person, with intent to deceive the listening or viewing public—
(1) To supply to any contestant in a purportedly bona fide contest of intellectual knowledge or intellectual skill any special and secret assistance whereby the outcome of such contest will be in whole or in part prearranged or predetermined.
(2) By means of persuasion, bribery, intimidation, or otherwise, to induce or cause any contestant in a purportedly bona fide contest of intellectual knowledge or intellectual skill to refrain in any manner from using or displaying his knowledge or skill in such contest, whereby the outcome thereof will be in whole or in part prearranged or predetermined.
(3) To engage in any artifice or scheme for the purpose of prearranging or predetermining in whole or in part the outcome of a purportedly bona fide contest of intellectual knowledge, intellectual skill, or chance.
(4) To produce or participate in the production for broadcasting of, to broadcast or participate in the broadcasting of, to offer to a licensee for broadcasting, or to sponsor, any radio program, knowing or having reasonable ground for believing that, in connection with a purportedly bona fide contest of intellectual knowledge, intellectual skill, or chance constituting any part of such program, any person has done or is going to do any act or thing referred to in paragraph (1), (2), or (3) of this subsection.
(5) To conspire with any other person or persons to do any act or thing prohibited by paragraph (1), (2), (3), or (4) of this subsection, if one or more of such persons do any act to effect the object of such conspiracy."
Note the repeated use of the word "intellectual" -- not physical. Therefore, this law does not apply to sports.
The Sports Bribery Act of 1964 which was passed to protect the "integrity" of sports from mafia and gambling interests. It reads: "Whoever carries into effect, attempts to carry into effect, or conspires with any other person to carry into effect any scheme in commerce to influence, in any way, by bribery any sporting contest, with knowledge that the purpose of such scheme is to influence by bribery that contest, shall be fined under this title, or imprisoned not more than 5 years, or both."
The key word in this law being "bribery." If a league instructs one of its employees -- be it an official, coach or athlete -- to influence and/or manipulate an outcome in a certain manner, such action does not break this law.
No one has been arrested for violating the Sports Bribery Act in relation to a professional sporting event -- ever.
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