OTTAWA -- Federal prison guards and other front-line correctional workers will not be allowed to use cannabis 24 hours before reporting to work.

The Correctional Service of Canada's policy on marijuana for employees comes a week before recreational cannabis use becomes legal.

The policy, made public today, says Correctional Service employees must be fit to perform their duties and cannot be intoxicated or impaired by drugs, alcohol or other substances when at work.

In addition, employees in "safety-sensitive" positions -- everyone from correctional officers who patrol the ranges up to wardens and the commissioner -- must refrain from cannabis use for a full day before work.

Managers will have to become familiar with signs a person is impaired or has been using pot.

Any breach of the policy may amount to a violation of the Correctional Service code of discipline and could lead to measures up to and including firing.