Found this bit searching around online, seems well-sourced and researched. I'd have to dig in to their sources a bit.
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I utilized my rights under the Freedom of Information Act passed by President Lyndon Johnson in 1966 to access over 40 years of FBI files on the NFL although some information was redacted. Here's what I found (this was written in 2013):
1. Contrary to popular belief and to what he NFL wants you to think, there have been fixed games in league history. On page 308 of Dan Moldea's book "Interference" he lists over 70 NFL games that have been fixed and includes the names of the 2 referees involved in fixing those games. He also lists interviews with NFL HOF players most notably KC Chiefs QB Len Dawson. He, in detail with documented facts supported by FBI documents, has interviews with NFL players and known gambling associates to uncover massive game fixing in the league. He also notes, with evidence, throughout the book that no fewer than 26 NFL team owners have or have had continuous and developing relationships with the gambling world, most notably the Rooney, Bidwill, and Mara families all getting their starts as Bookmakers for established mid-west crime families and buying their NFL franchises with moneys earned from gambling. So that in and of itself is a hypocrisy number 1 on the NFL's "lilly white" reputation.
NFL Referees are part-time employees of the NFL. They are not employees of any team nor do they get paid anywhere close to the sums of NBA refs. NFL refs make between $25K to $70K per season. They work for the league and do what the league tells them to do. They are not there for "the integrity of the game". Referees, unlike other sports, are bound by NFL mandated gag orders which prevent them from talking to the media.
2. The NFL possesses an Anti-Trust Exemption to the law granted to it by President John F. Kennedy, which ultimately allows the NFL to classify itself as "entertainment" rather than sport, as well as incorporate itself as a single entity instead of the 32 separate "franchises" they would want you to believe. Contrary to the perception of the NFL being 32 separate franchises battling it out for gridiron supremacy. In a franchised environment, such as McDonalds (Business 101), each franchise is individually owned and operated and can participate in national promotions, have its own local promotions, or abstain from participating (hence the fine print in commercials saying "at participating locations".
This keeps the regionality of competition in tact without having to compete on a national level. MLB has this status, the NFL does not. Instead, since the NFL has this Anti-Trust exemption, it is able to package its teams in order to sell to national television companies, which today totals $6 Billion in revenue for the league. That is 75% of the leagues total annual revenue. In a 2004 lawsuit vs the NFL, the NFL attorney Gregg H. Levy argued that "the NFL is not a collection of 32 individual teams, but rather a single entity. And as long as the NFL teams are a unit, and they compete as a unit in the entertainment marketplace, then they should be deemed a single unit and not subject to any Anti-Trust laws."
There is only another "sports" organization that I can think of that follows this, the WWE. Levy also argued that the league markets its products and merchandise as a whole to promote the NFL as a whole. These arguments led all the way to lockout during the 2011 offseason. The league would still earn $5 Billion in revenue, even without a single game being played.
Professional sports is the only industry without ANY federal oversight. Therefore the league can do and go as they see fit, this is something the players were concerned about going into the lockout, the NFL players themselves sought help from US Congress asking for oversight of the NFL. And NFL players wanted an explanation as to why the NFL owners were granted an Anti-Trust exemption in the first place. They didn't get it.
The NFL proved in this lawsuit that they see themselves as a single unit in the "entertainment" industry and the unique league revenue sharing strategy is not common amongst professional sports leagues.