Bell has been part of Stage 1 of the program since last September, when he was arrested on drunk driving and hit and run charges in California.
The 27-year-old pleaded no contest to the charges last month. He is due to serve six months in a California county jail at the end of the 2007-08 NHL season.
The native of St. Paul, Ont., has said he hasn't had a drink since the incident.
"He's been under good care, he's fully complied with all of the testing through the year," said Leafs GM John Ferguson. "It's my understanding that the Stage 2 process is related . . . to the plea arrangement."
Bell will not be paid during his suspension and will need the approval of both the NHL and the NHLPA, after consultation with program doctors, before being reinstated. There is no timeline on when that might be.
Players enrolled under Stage 1 of the substance abuse program are able to continue playing while those in Stage 2 can not.
Bell's agent Larry Kelly says his client has had no trouble complying with the program during the past year.
"This has been actually a very good story," said Kelly. "It's been a life-changing event for Mark.
"Mark has done absolutely everything asked of him. He's co-operated in every way. I think he's really benefitted from the program to date."
Toronto opens training camp Sept. 13. The substance abuse program doctors will make a "clinical determination" about which training camp activities he'll be allowed to participate in.
The Maple Leafs acquired Bell in June along with goaltender Vesa Toskala in a trade with the San Jose Sharks.
"We were aware of the charges of the incident and also of the fact that he'd been fully compliant of the program through the year and had not failed a single test," said Ferguson. "He's had a whole season of positive decision-making."