I wonder what their legal arrangement is exactly. They certainly have not collectively bargained with the league. I would guess they have a contract with the club, although who knows at this point what the status of that contract is. And, more importantly, who knows what kind of restrictions that agreement puts on them viz. the league itself. I don't necessarily assume it precludes them from suing the league, because why would it -- who would anticipate that situation?
So, it sets up a potentially interesting legal dynamic, though it seems to me very unlikely it would ever come to it. But imagine Vincent says, "you must accept the findings of the Wells report," and they say, "respectfully, Mr. Vincent, we cannot do that, because it's not true." And so the league forbids them from working for the Patriots. And I have no doubt that if the NFL invoked that, there must be some agreement between the NFL and the clubs that would mean the Patriots have to comply. But if the team was otherwise willing to employ them, I'm not so sure they wouldn't have some sort of tortious interference claim against the league.