A provincial review board has decided that Vince Li can be given supervised time outdoors, but Manitoba's Attorney General said that won't happen until security is tightened at the facility where Li is being housed and treated for mental illness.

Li was found not criminally responsible for beheading Tim McLean in 2008 on a Greyhound bus. Li has been housed inside the Selkirk Mental Health Centre since the court's ruling last year.

In the review board's decision released Thursday, it said it took into consideration evidence from Li's treatment staff along with victim impact statements and consideration of the public's safety.

At a hearing on Monday, doctors treating Li asked the review board to allow him supervised outings in an outside courtyard which would give him access to fresh air for 15 minutes every day.

The review board granted permission for Li to be given supervised time outside on the grounds of the centre, subject to a number of conditions, including that his treatment staff hold the opinion that his condition is stable enough for him to leave a locked ward.

The board also said he is to be escorted at all times by two staff members who are equipped with a cell phone or two-way radio.

Li's time outside will be start with 15 minutes and increase to a maximum of one hour, twice daily, said the review board.

Security staff also have to be informed when Li is given time outside.

If Li is required to leave the grounds of the centre for any reason, a peace officer must escort him, said the review board.

The review board's order regarding Li's supervised time outside takes effect on June 7.

However, Manitoba Attorney General Andrew Swan said Li will not be allowed to leave the locked forensic unit of the Selkirk facility until additional security measures are in place.

"This order is contrary to the interests of public safety, and seriously undermines public confidence in the Canadian system of Justice," Swan said.

Swan would not say what additional security measure will be put in place, but said all options would be considered, including looking into the order itself.

The hospital will be presenting the enhanced security options and one option that will be looked at is fencing this entire hospital, Swan said.

John Stefaniuk, Chair of the Manitoba Review Board, said he is prohibited from discussing specific cases, but said that, in general, the parole board does not take the public's reaction to decision into account.

"The risk to the public is certainly a paramount consideration," Stefaniuk said. "That's different than perception. We look at the actual risk and we look at the recommendations that we receive, and the evidence as to the patient's mental condition, and the risk of danger to the public including the patient him or herself."

Carol de Delley, the mother of Tim McLean, said she worries Li will eventually be freed.

"Put him in a locked facility, build a facility that can house individuals that are this dangerous, and leave them there for the rest of their days," de Delley said.

- with files from CTV's John Hendricks