Sources familiar with the the collusion case, which is being fought behind closed doors, told Yahoo Sports that Kaepernick's lawyers will seek the subpoena in the next few weeks. Subpoenas compel a person to testify in court in what is called a deposition.
In order to secure a subpoena, Kaepernick's legal team will have to convince the system arbitrator that forcing Trump to testify is justifiable and important to the NFL player's grievance case. The athlete has accused NFL team owners of conspiring with one another to keep the former San Francisco 49ers quarterback from being signed to a team again, ending his football career.
Kaepernick had been signed to the 49ers since the 2011 season, but despite leaving the team in March 2017, he has not been signed by anyone else. Allegations that he was blackballed from the league for his high-profile and highly controversial on-field protests against police brutality, which saw him kneeling during the US national anthem, have roiled ever since. Kaepernick's defenders say the quarterback is more than qualified to lead a team, and that the only explanation for his lack of a contract is his political stance.
Some Americans, including Trump, have called Kaepernick's protests an affront to the military and the flag of the United States, although Kaepernick has consistently denied that either was a target of his demonstrations..
The president spoke directly to a number of team owners, with at least one, Miami Dolphins owner Stephen Ross, saying that Trump had influenced him to rescind his support for players who protested during the anthem. Statements like these could prove vital in securing a subpoena against the president in the collusion case.
Meanwhile, Dallas Cowboys owner Jerry Jones said during his own deposition in this case that Trump had told him to "Tell everybody [in the NFL] ‘you can't win this one.'"
New England Patriots Owner Robert Kraft even joined Trump on an Air Force One flight in March 2017. The following day, Trump boasted at an event in Kentucky that NFL owners were staying away from Kaepernick out of fear of getting "a nasty tweet from Donald Trump."
If Kaepernick's legal team is successful in their arguments before the system arbitrator, they could also depose Trump associates that are familiar with his behavior affecting the case.
That could include Vice President Mike Pence, whose walkout protest of a 49ers game in October (some time after Kaepernick's departure) after players kneeled during the national anthem Trump admitted to having orchestrated.
The president is implicated in the case in a number of other ways, but that doesn't mean that Kaepernick's attorneys will necessarily be successful in getting him deposed, as Trump's team has repeatedly made statements indicating their unwillingness to comply with other subpoenas, such as those connected to the investigation of special counsel Robert Mueller. Trump's lawyers have argued that his position as commander-in-chief shields him from standard legal proceedings.