NFL Commissioners and coaches do have SOP's (contracts) with pretty clear dictates. The problems have always arisen however when sometimes they "feel like" enforcing parts of it and sometimes they don't which naturally causes confusion and claims of preferential treatment, bias, harassment, etc. There are examples of some wanting to be more "individualistic" with the color of their cleats, wearing certain stickers on their helmets, etc. in the past. If there's no consistency, there's chaos. Some people here posted this over the last couple of days:
The specific rule pertaining to the national anthem is found on pages A62-63 of the NFL League Rulebook. It states:
“The National Anthem must be played prior to every NFL game, and all players must be on the sideline for the National Anthem.
“During the National Anthem, players on the field and bench area should stand at attention, face the flag, hold helmets in their left hand, and refrain from talking. The home team should ensure that the American flag is in good condition...
...It should be pointed out to players and coaches that we continue to be judged by the public in this area of respect for the flag and our country. Failure to be on the field by the start of the National Anthem may result in discipline, such as fines, suspensions, and/or the forfeiture of draft choice(s) for violations of the above, including first offenses
