The NFL sent out a document outlining its social media policy for teams and players. The statement includes a prohibition against using social media or social networking sites like Twitter and Facebook during games. This restriction begins 90 minutes before the game starts and ends after the player finishes post-game media interviews. So, no tweets at halftime.
That part makes sense. You want football players to be concentrating on football, not Twitter. And you want to avoid game day turning into a circus.
The statement also included a restriction to the media and websites from producing a play-by-play description of NFL games, a prohibition that seems targeted specifically at Twitter.
"Longstanding policies prohibiting play-by-play descriptions of NFL games in progress apply fully to Twitter and other social media platforms. Internet sites may not post detailed information that approximates play-by-play during a game. While a game is in progress, any forms of accounts of the game must be sufficiently time-delayed and limited in amount (e.g., score updates with detail given only in quarterly game updates) so that the accredited organization's game coverage cannot be used as a substitute for, or otherwise approximate, authorized play-by-play accounts."
This area seems aimed squarely at accredited newspapers, magazines and websites. I'm not a lawyer, but my understanding of copyright law is that facts cannot be copyrighted, so if a company wants to send play-by-play descriptions of NFL games to Twitter, there isn't much the NFL can do about it other than revoke press access. And I wouldn't be surprised if we see some play-by-play on Twitter. After all, we'll get it from fans if nothing else.