I pulled it up. As you know, we live to serve. The collective bargaining agreement has a whole chapter on collusion. The pertient part:
Ch. 17: Collusion Section 1. Prohibited Conduct:
(a) No Club, its employees or agents shall enter into any agreement, express or implied, with the NFL or any other Club, its employees or agents to restrict or limit individual Club decision-making as follows:
(i) whether to negotiate or not to negotiate with any player;
(ii) whether to submit or not to submit an Offer Sheet to any Restricted Free Agent;
(iii) whether to offer or not to offer a Player Contract to any player;
(iv) whether to exercise or not to exercise a Right of First Refusal; or
(v) concerning the terms or conditions of employment offered to any player for inclusion, or included, in a Player Contract.
No Club may have a policy not to negotiate with, or enter into a Player Contract with, any player who is free to negotiate and sign a Player Contract with any Club, on any of the following grounds, if such policy is inconsistent with Section 1 above:
(a) that the player has previously been subject to the exclusive negotiating rights obtained by another Club in a College Draft, by virtue of a Required Tender to a player with less than three Accrued Seasons, or a Franchise Player designation; or
(b) that the player has refused or failed to enter into a Player Contract for a prior season containing a Right of First Refusal or an option clause (i.e., any clause that authorizes an extension or renewal by a Club of a Player Contract beyond its stated term);
(c) that the player has become a Restricted Free Agent or an Unrestricted Free Agent; or
(d) that the player is or has been subject to any Right of First Refusal.
Section 3. Club Discretion:
Section 2 above does not diminish any Club’s right not to negotiate or contract with any particular player on any policy ground not specified above. In conjunction with other evidence of an alleged violation(s) of Section 1, a Club’s adherence to a policy identified in Section 2 above may be offered as evidence of an alleged violation of Section 1 above, but may not be the basis of any separate proceeding seeking any penalty or other relief against any Club or the NFL.
The person claiming collusion has to prove his case by a "clear preponderance of the evidence" and that preponderance of the evidence has to be based on something more than the player's skills and the fact that he wasn't offered a contract. This is at Art. 17 sections 5 and 6.
What does all this mean?
Clubs have to talk to a player's agents, and consider the player, but are not under any obligation to sign that player. Clubs cannot reach an agreement with other clubs not to sign the player. I think there can be a grievance if either the clubs won't negotiate with a player or if there is an agreement not to sign a player. In Kaepernick's case, his lawyer said that they negotiated with all thirty two teams, and were filing the grievance under a collusion theory.
The grievance itself is not public. That means we don't get to see the smoking E-mail where every team agreed not to sign Kaepernick despite his overpowering football skills. Maybe there is such an Email. I doubt it. If there was, the lawyer, Gregarious would have said so during his press conference. He talked about Donald Trump instead.
I think that Kaepernick's case is probably a loser unless he has awesome evidence that his swaggering lawyer didn't mention. (The chances of that are nil) I think that filing a grievance is probably a good idea if he wants another NFL job, but a bad idea if he wants to avoid being ridiculed for fifty years. The grievance is a good idea because Kaepernick has stayed unemployed through the whole season. Doing nothing hasn't worked out for him. He is retired unless he does something splashy. A grievance keeps him in the public perception, and maybe a team that needs a backup quarterback, or one that needs a shot of political correctness will give him a job. All publicity is good publicity.
The grievance is a bad idea because he will lose, and all the fans will remember him as the guy who was known more for his girlfriend's tweets than his play.
I think that the truth of the matter is that Kaepernick never showed himself to be a next level special talent when he was a starter, he was caught drinking and smoking marijuana, and he started the anthem protest and opted out of a contract without having some other job lined up. A quarterback is like an extra coach and a leader in the club house. If the drama becomes too extreme, teams can pass because there are a lot of talented guys who will do what the org says and give a kidney for a backup QB job. Also, there aren't that many QB jobs to be had. Anyone in a special field will suffer severe repercussions for burning his bridges.
My two cents.