Cowboys owner Jerry Jones has been on the record in saying that he would not play a player if they knelt during the national anthem.
However, at this point, there is not a policy forbidding players in the NFL from kneeling during the national anthem.
Here is a joint statement from NFL-NFLPA today about the national anthem:
“Commissioner Roger Goodell reached out to NFLPA Executive Director DeMaurice Smith today and both he and player leadership will attend the League meetings next week. There has been no change in the current policy regarding the anthem. The agenda will be a continuation of how to make progress on the important social issues that players have vocalized. Everyone who is part of our NFL community has a tremendous respect for our country, our flag, our anthem and our military, and we are coming together to deal with these issues in a civil and constructive way.”