I can imagine they’re using the loophole that NFL stadiums were built with public money, and that NFL games go over public airwaves. Or something, I don’t know.
This is one reason that tax payer money should not be used to build stadiums. Secondly, the NFL is not using public airwaves, the networks are. The broadcast companies are the ones who license the content. When the NFL tried to offer content on their private network the politicians decided to step in and the NFL was strong armed into making the game available on broadcast TV.