There are not. The best they’ve got is the personal conduct policy, but having let it go for a year and a half there’s no way they’ll be able to apply it now. Anthem behavior is not codified in the rulebook, not for any of the sports leagues except the NBA (who put it in place the same time Stern gave them a dress code for entering the arena, I never liked Stern but he sure knew which way the wind was going to blow). The NFL has to put up with it.
Looks like the owners need better lawyers. Simple solution, “Any and all behavior by employee that embarrasses, threatens, etc. the brand and or value of the Owner's asset will lead to the suspension and or termination of employee.” I'm not a lawyer. At this point I forward my demand to Legal Staff.