"Haupt owns the recording but not its content, which belongs to the N.F.L. If the league refuses to buy it, he cannot sell the tapes to a third party, like CBS or a collector who would like to own a piece of sports history that was believed to be lost."
Copyright law does not (as far as I understand it) actually give someone "ownership" of a work. Rather, it criminalizes making copies of the work without the permission of the copyright owner. But the author of a book cannot prevent you from selling your copy to a library, a friend, or a rich collector.
My view would be that Troy Haupt ought to be able to sell his videotape to anyone he wants (just as he could sell a book). He ought to be able to show the content to anyone he wants (although a "public performance" is a different matter). If the NFL complains that the copy was made illegally, then they should sue Mr. Haupt's father (or his presumably long-settled estate).
Perhaps the legal theory here is that the NFL never authorized the recording so it's existence is the equivalent of stolen property?