NFL commissioner Roger Goodell has reinstated Miami Dolphins running back Ricky Williams from an 18-month suspension.

Williams had been suspended for repeated violations of the league's substance abuse policy.

Williams can begin practising with the team immediately, although he will not be eligible to play in a game until November 26 at Pittsburgh.

It is uncertain if the Dolphins will even allow Williams to return. In May, Dolphins first-year coach Cam Cameron made it known that he would not be open to Williams returning.

"The easiest predictor of future behaviour is previous behaviour Cameron said. "Ultimately, it comes down to the team. You want to be as fair as you can be, but no individual comes above the team."

At 0-9, the Dolphins are off to their worst start in franchise history. With Ronnie Brown (knee) out for the season, the Dolphins have been using Jesse Chatman as their featured back.

Williams was suspended for the entire 2006 season after violating the league's substance abuse policy for the fourth time. After again testing positive for marijuana, he was not able to apply for reinstatement until this past September.

Williams, 30, then spent the 2006 campaign with the Toronto Argonauts of the Canadian Football League. The Argonauts signed Williams to a one-year contract after receiving permission from the Dolphins.

In 14 games for Toronto, Williams rushed for 526 yards, averaging 4.8 yards per carry, and two touchdowns. He also caught 19 passes for 127 yards.

After stunning the football world by announcing his retirement during training camp in July 2004, Williams returned to the NFL in 2005 and rushed for 743 yards and six touchdowns for Miami while splitting time in the backfield with Brown.

Williams missed the first four games of the 2005 season and was fined for the second and third violations of the substance abuse program. Those positive tests occurred in December 2003 and in the 2004 off-season.