Jackson was controversially cut by the Eagles last Friday shortly after reports surfaced linking him to a Los Angeles gang.
The 27-year-old, who has since signed with the Washington Redskins on a three-year contract, denies the reports, and the NFLPA now plans to look into the situation in an attempt to 'protect the integrity' of the player.
"That's something that we're going to look at. We've always been aggressive about protecting the integrity of our players, especially where we believe or think that a team may have done something that is impermissible, and that's something that we're gonna look at," NFLPA executive director DeMaurice Smith told ESPN.
"You're talking to a guy who spent 10 years as a federal prosecutor in Washington, DC, and I grew up in the city, to have someone come out and say 'gang affiliation,' I'm not sure I know what that means. I certainly know what it means to prosecute members of a gang. I certainly know what it means to be a member of organized crime. I don't know what it means when a team or an official says that there's 'gang affiliations.'
"To me, the real issue is this is the business of football. If you want to make a decision to cut a player, tell a player he's cut. Make a decision. But if you want to smear a player with innuendo or something that is less than proof, you know that I was very aggressive in calling a few GMs cowards for what they said about a young man coming out of college [former Missouri defensive end Michael Sam]. It seems to me that the same thing applies, if you want to smear someone and you don't have any evidence."
Jackson posted career-high figures of 82 receptions for 1,332 yards and nine touchdowns last season, earning him a place in the Pro Bowl for the third time.