Attorneys for quarterback Colin Kaepernick have notified the NFL that they are requesting that several team owners, including the Dallas Cowboys’ Jerry Jones and Houston Texans’ Robert McNair, participate in depositions as part of Kaepernick’s grievance accusing owners and teams of colluding to keep him out of the league, a person familiar with the case said Friday.

The request also seeks access to electronic communications, including emails and text messages, involving several teams that were linked to Kaepernick, according to that person, who spoke on the condition of anonymity because Kaepernick’s grievance remains pending.

The NFL declined to comment. Several of the teams involved either declined to comment or did not immediately respond to requests for comment.

Kaepernick has remained unsigned since opting out of his contract with the San Francisco 49ers following last season. He began the movement of players protesting during the national anthem while with the 49ers last season. He is being represented in his collusion grievance by Los Angeles-based attorney Mark J. Geragos, with support being offered by the NFL Players Association.

Geragos declined to comment on the specifics of the case or the request for depositions and electronic communications but said in a brief phone interview: “Every day that goes by and he doesn’t get signed is another nail in the NFL’s defense.”

If the case reaches a hearing, it would be heard and resolved by Stephen B. Burbank, a University of Pennsylvania law professor who resolves disputes between the league and players’ union arising from their collective bargaining agreement.

Under the terms of the CBA, Kaepernick must prove that teams conspired with each other or with the league. The fact that he remains unsigned, in comparison to players who have been signed and are on rosters, does not by itself prove collusion, under the agreement.

Jones has said he would bench any Cowboys player who protest during the anthem. McNair created a controversy when he reportedly said during a recent owners’ meeting that the NFL “can’t have the inmates running the prison.”

The request by Kaepernick’s legal team was previously reported by other media outlets, including CBS and ESPN. Those reports also mentioned Jed York of the 49ers, Paul Allen of the Seattle Seahawks and Robert Kraft of the New England Patriots among the owners who could be deposed, and the Seahawks, Tennessee Titans and Baltimore Ravens among the teams from which electronic communications are being sought.

Kaepernick had a visit with the Seahawks during the offseason but was not signed. The Ravens reportedly considered signing him during training camp when their starter, Joe Flacco, was managing a back injury, but did not. The Titans signed Brandon Weeden instead of Kaepernick during the season when starter Marcus Mariota was hurt.

Kaepernick opted out of his contract with the 49ers but the team has said it would have released him rather than retaining him under the terms of that deal.

The NFLPA did not respond to a request for comment Friday.

Legal experts say that collusion cases are difficult to prove without a “smoking gun” of evidence that teams conspired with each other or with the league.

“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,” the CBA says, adding that applies to “whether to negotiate or not to negotiate with any player” and “whether to offer or not to offer a Player Contract to any player,” among other things.

The CBA also says: “The failure by a Club or Clubs to negotiate, to submit Offer Sheets, or to sign contracts with Restricted Free Agents or Transition Players, or to negotiate, make offers, or sign contracts for the playing services of such players or Unrestricted Free Agents, shall not, by itself or in combination only with evidence about the playing skills of the player(s) not receiving any such offer or contract, satisfy the burden of proof set forth … above.”