nfl protests trump zw js orig_00001313.jpg
nfl protests trump zw js orig_00001313.jpg
Now playing
02:26
#TakeAKnee heats up on and off the field
Miami Dolphins wide receiver Kenny Stills (10) and Miami Dolphins wide receiver Albert Wilson (15) kneel during the national anthem before an NFL football game against the Tennessee Titans, Sunday, Sept. 9, 2018, in Miami Gardens, Fla. (AP Photo/Wilfredo Lee)
PHOTO: Wilfredo Lee/AP
Miami Dolphins wide receiver Kenny Stills (10) and Miami Dolphins wide receiver Albert Wilson (15) kneel during the national anthem before an NFL football game against the Tennessee Titans, Sunday, Sept. 9, 2018, in Miami Gardens, Fla. (AP Photo/Wilfredo Lee)
Now playing
01:47
Two Miami Dolphins kneel for National Anthem
PHOTO: From Instagram
Now playing
00:36
Nike ad features Colin Kaepernick
trump nfl anthem comment george martin sot newday_00002109.jpg
PHOTO: Fox News
trump nfl anthem comment george martin sot newday_00002109.jpg
Now playing
01:34
Trump: Maybe players who kneel shouldn't be in US
Philadelphia Eagles
PHOTO: Michael Perez/AP
Philadelphia Eagles' Zach Ertz kneels before an NFL football game against the Chicago Bears, Sunday, Nov. 26, 2017, in Philadelphia. (AP Photo/Michael Perez)
Now playing
01:10
Eagles star rips Fox News report
PHOTO: CNN
Now playing
02:25
Panelist: Trump lives to divide our country
george martin nfl anthem decision reaction sot newday_00000000.jpg
PHOTO: CNN
george martin nfl anthem decision reaction sot newday_00000000.jpg
Now playing
01:52
Ex-NFLer: Anthem decision was misguided
PHOTO: CNN
Now playing
01:38
Steve Kerr: NFL using anthem as fake patriotism
PHOTO: Comedy Central
Now playing
01:10
Late night weighs in on Trump's NFL remark
CNN host Van Jones interviews Shawn "Jay-Z" Carter on the first episode of "The Van Jones Show" on Saturday, Jan. 27, 2018 in New York, NY.

Photo by John Nowak/CNN
PHOTO: John Nowak/CNN
CNN host Van Jones interviews Shawn "Jay-Z" Carter on the first episode of "The Van Jones Show" on Saturday, Jan. 27, 2018 in New York, NY. Photo by John Nowak/CNN
Now playing
01:24
Jay-Z: Colin Kaepernick 'an iconic figure'
SANTA CLARA, CA - SEPTEMBER 12:  Colin Kaepernick #7 and Eric Reid #35 of the San Francisco 49ers kneel in protest during the national anthem prior to playing the Los Angeles Rams in their NFL game at Levi
PHOTO: Thearon W. Henderson/Getty Images North America/Getty Images
SANTA CLARA, CA - SEPTEMBER 12: Colin Kaepernick #7 and Eric Reid #35 of the San Francisco 49ers kneel in protest during the national anthem prior to playing the Los Angeles Rams in their NFL game at Levi's Stadium on September 12, 2016 in Santa Clara, California. (Photo by Thearon W. Henderson/Getty Images)
Now playing
01:16
Kaepernick's attorney speaks out on grievance
PHOTO: Dennis Bernstein The Fourth Period @DennisTFP
Now playing
01:04
NFL stars sit during national anthem
LOUISVILLE, KY- MARCH 20: U.S. President Donald Trump holds a rally in Freedom Hall at the Kentucky Exposition Center March 20, 2017 in Louisville, Kentucky.  (Photo by Bill Pugliano/Getty Images)
PHOTO: Bill Pugliano/Getty Images
LOUISVILLE, KY- MARCH 20: U.S. President Donald Trump holds a rally in Freedom Hall at the Kentucky Exposition Center March 20, 2017 in Louisville, Kentucky. (Photo by Bill Pugliano/Getty Images)
Now playing
00:44
Trump: NFL is scared of my tweets
SANTA CLARA, CA - SEPTEMBER 12:  Colin Kaepernick #7 and Eric Reid #35 of the San Francisco 49ers kneel in protest during the national anthem prior to playing the Los Angeles Rams in their NFL game at Levi
PHOTO: Thearon W. Henderson/Getty Images North America/Getty Images
SANTA CLARA, CA - SEPTEMBER 12: Colin Kaepernick #7 and Eric Reid #35 of the San Francisco 49ers kneel in protest during the national anthem prior to playing the Los Angeles Rams in their NFL game at Levi's Stadium on September 12, 2016 in Santa Clara, California. (Photo by Thearon W. Henderson/Getty Images)
Now playing
00:57
NFL star continues national anthem protest
(CNN) —  

Colin Kaepernick’s legal team is expected to seek subpoenas for President Donald Trump, Vice President Mike Pence and other campaign officials relating to the quarterback’s collusion case against the NFL, a source familiar with the ongoing grievance process has told CNN.

The new move intends to explore NFL owners’ ties with Trump, the source said, adding that several owners, as well as NFL Commissioner Roger Goodell, have already been deposed in the case.

Brian McCarthy, a spokesman for the NFL, said the league had no comment. The expected move was earlier reported by Yahoo! Sports.

Kaepernick ignited a controversy back in 2016 when he refused to stand during the National Anthem, protesting what he believes are racial injustices and ongoing police brutality in the US. He opted out of his contract with the 49ers last year and became a free agent, but no NFL team has signed him. He filed a grievance against the NFL in October, claiming teams are colluding to deny him a job.

The anthem controversy, meanwhile, has ignited a racially sensitive national debate over free speech, pitting mostly black athletes against white NFL owners, and Trump has seized on the issue to energize his political base.

At a rally in Louisville, Kentucky, last year, Trump switched gears from talking about the nation’s urban communities to calling out the quarterback.

“It was reported that NFL owners don’t want to pick him up because they don’t want to get a nasty tweet from Donald Trump,” he said. “Do you believe that?”

Trump also has called out the NFL multiple times over the anthem controversy. He canceled the traditional visit by the Super Bowl champion Philadelphia Eagles earlier this week, initially claiming that the decision was due to players not standing for the anthem, though the White House later acknowledged that low expected attendance by team members was a key factor.

Pence left an October NFL game between the 49ers and Colts in Indianapolis after some players knelt during the National Anthem, saying on Twitter at the time that he would not “dignify any event that disrespects our soldiers, our Flag, or our National Anthem.”

Last month, NFL team owners decided that players must stand during the National Anthem this season, a reaction to fierce backlash against some who took a knee in symbolic opposition to what they view as the systemic oppression of people of color, including by police.

Goodell said teams whose players and personnel do not stand and show respect for the flag and the anthem will be fined by the league. Each team, however, may develop its own work rules for those who don’t comply with the policy, which allows players the option of remaining in the locker room during the playing of the anthem if they do not wish to comply.