NFl rules state teams can only use footage provided by the NFL, ie all their game tapes must be provided by the nfl from the booth. These tapes are edited to insure fairness by only showing teams what the other teams do ON the field.
"This telecast is copyrighted by the NFL for the private use of our audience. Any other use of this telecast or of any pictures, descriptions, or accounts of the game without the NFL’s consent, is prohibited.
It is illegal to tape ANY footage of a game without the NFLs consent.
There are also rumors now that the patriots illegally taped the rams walkthrough practive before the 2001 superbowl, the one that started the 'dynasty'.
Now the govt. is getting in on it because football is a sanctioned betting event and covered by federal anti-trust laws. Should a team be caught cheating a federal investigation would be started to see exactly how much for how long. An investigation which could cause major problems for the NFL and team owners. Good thing the comissioner had all the evedence destroyed before the investigation could start.....or the comissioners excuse "so the patriots couldn't get the tapes back.....ever heard of a safe?
Also, keep in mind that a lot of non gambling money rides on these games. Everything from player salaries and bonuses, team bonuses, endorsements, merchandise, etc.....