Per ESPN's Ed Werder, Smith will be eligible to take part in team activities after being reinstated by commissioner Roger Goodell.
Smith last played in a game on Nov. 15, 2015, two days before the NFL handed down a one-year suspension for violating the league's policy on substances of abuse.
Three months earlier, while he was still a member of the San Francisco 49ers, Smith was arrested in Santa Clara, California, on charges of hit and run and driving under the influence. The 49ers subsequently released the troubled linebacker, and he signed a one-year deal with the Raiders in September.
As part of Smith's suspension, he had to apply for reinstatement to the NFL. Former Raiders general manager Reggie McKenzie told Vic Tafur of the San Francisco Chronicle about the process of trying to get Smith back into the league in October 2016.
"Aldon is doing well," McKenzie said. "That situation is going to be totally up to the league because he's been in the program and they've monitored him. It's up to Goodell to say, 'Yea, nay or when.' And he could say no to everything. ... That part is out of our hands."
The situation got more complicated in February 2017 when TMZ Sports reported Smith was under investigation by San Francisco police for alleged domestic violence, though he was not arrested. NFL spokesman Brian McCarthy said at the time the league was "looking into the matter" in an email to Jerry McDonald of the San Jose Mercury News.
Smith was arrested in March 2018 after turning himself over to San Francisco police for violating a restraining order related to the domestic violence allegation. He was booked on three misdemeanor charges
At this point in his life and career, no one knows what Smith will be able to add on the field. He's walking into a situation with the Cowboys where he doesn't have to play a significant role. The defensive line already features Demarcus Lawrence, Gerald McCoy, Dontari Poe and Dorance Armstrong.
As long as Smith has turned over a new leaf, he could be a productive pass-rusher in 2020. This is a huge roll of the dice for Dallas, but the payoff is getting a tremendous talent on a cheap contract who helps the team get back to the postseason.