The NIT has charged that the NCAA violated antitrust law when it threatened to sanction teams who declined an invitation to the NCAA tournament in favor of the NIT. Jeffrey Kessler, an attorney representing the NIT, states his case in the NY Times.
In 1950, for example, City College of New York played in and won both tournaments.
In 1962, Loyola, Mississippi State, Dayton, the University of Houston and St. John's all chose to participate in the N.I.T. rather than accept invitations to the N.C.A.A. tournament. In 1970, Marquette, one of the best teams in the nation that year, chose to go to the N.I.T. over the N.C.A.A. tournament, which provoked an outcry by the powers that ran the N.C.A.A. tournament. .....
[I]n the early 1980's, [the NCAA] took decisive action.
The N.C.A.A. changed its rules so that all schools invited to its tournament would be required to boycott the N.I.T. under the pain of N.C.A.A. penalties, and combined that rule with a major expansion of the N.C.A.A. tournament field to 64 teams from 32. The result is that each year the N.I.T., or any other tournament that may try to enter the market, is prevented from competing for any of the best teams in the country, and the N.C.A.A.'s monopoly power and profits are assured.
The NIT may have a very good case. I do not object to the NCAA's effective monopoly in the tournament in any way shape or form, but a boycott requirement violates antitrust law. A simple requirement that a school commit to the NCAA tournament if an invitation were accepted would have been sufficient, and lawful. The NCAA, by the way, is a serial violator of the Sherman Antitrust Act, so this is nothing new. But the NIT is woefully slow in suing over something that occurred twenty years ago.