He played in 2015 with the Raiders before he was banned.
According to TMZ, the troubled linebacker is being investigated for an alleged domestic violence incident that occurred at a house in San Francisco early Saturday morning.
The specifics of what exactly happened are unknown.
During his tenure with the 49ers, Smith was arrested five times in three years.
The Raiders linebacker has been out of football since November 17, 2015, when the NFL suspended him for one year for violating the league's substance abuse policy.
The police report could potentially delay the March reinstatement, with the long-term ramification potentially being an indefinite suspension which would put Smith out of the league for another year or more. Although Smith hasn't been charged with anything, a police source did tell TMZ that a report was taken and the case is under "active investigation".
Smith filed for reinstatement on October 3 before meeting with commissioner Roger Goodell. It tolled in 2016 despite him never playing a game, meaning he has one year left on his deal with the Raiders.
"I'm back, and there's nobody who can stop me", Smith said on a video.
Aldon Smith might be all done in Oakland.
The reason it's been so hard for Smith to get reinstated is because he has a prior history. He was released by the Niners in August 2015 following his fifth arrest since 2011 and third on suspicion of drunken driving.
Smith also was suspended for nine games in 2014.
"We are looking in to the matter", National Football League spokesman Brian McCarthy said in an e-mail Tuesday.