A recent Ontario labour arbitration decision provides helpful guidance for employers managing cannabis use in safety-sensitive workplaces. In MSC Toronto o/a Continuous Colour Coat Limited v United Steelworkers Local 3950-65, the arbitrator concluded that the employee had consumed cannabis during his lunch break and returned to work contrary to company policy. However, while the policy breach was established, the employer did not adduce sufficient evidence to prove observable impairment. As a result, and taking into account the employee’s nine years of service, the termination was set aside and substituted with a three-month unpaid suspension.