The delay, first reported by Pro Football Talk, came after Smith applied for reinstatement following a one-year suspension for violating NFL rules on substance abuse.
Smith's yearlong suspension was due to end Nov. 17, and he applied for reinstatement Oct. 3.
"A little disappointed, honestly," Raiders coach Jack Del Rio said of the decision. "I feel like from everything that I've gathered, obviously it's not my job to make a rule, but from everything I've gathered, he's done his duty to take care of all the things he needs to take care of. I see some of the guys that have been allowed back. My question is, What's the difference? It's always a question mark. If a guy has a chance, he should have a chance to make a living. I don't really agree with what's gone down, but it's not my job. We'll move on as a team. That's what we have to do, but I'm a little disappointed."
Commissioner Roger Goodell said earlier this month that there was no timeline for any resolution on Smith's case. Goodell also said he had met with the linebacker.
Smith's suspension fell "under the collectively bargained substances of abuse policy" and thus "the player must provide all documentation and follow the procedures set forth in the policy," NFL spokesman Brian McCarthy wrote in a November email.
According to ESPN NFL Insider Adam Schefter, Smith spent 120 days at a rehabilitation facility, starting on July 29, after a Periscope video on an account purportedly belonging to Smith showed an unidentified man and woman talking about a hand-rolled cigarette. Smith denied it was him in the video, which was posted over the summer.
The NFL was going to investigate the video, according to ESPN's Ed Werder, because it might have violated the terms of Smith's suspension.
The Raiders, who could have no formal contact with Smith under the terms of the suspension, re-signed him to a two-year contract in April after his 3.5 sacks in nine games for Oakland in 2015.