In the recent decision of Lower Churchill Transmission Construction Employers’ Association and IBEW, Local 1620, arbitrator John Roil, QC, dismissed a grievance where an employer, Valard Construction LP (the “Employer”) refused to hire an employee using medical cannabis, on the basis of undue hardship.


The Grievor applied for the position of Utility Person on the Churchill project with the Employer. The Grievor used medical cannabis to manage pain relating to osteoarthritis and Crohn’s Disease. The medical cannabis had been prescribed by the Grievor’s physician after attempts at treating his pain with conventional treatments had been unsuccessful.  The Grievor ingested 1.5 grams of cannabis at a THC level of less than 20% each evening, through vaporization.

The job that the Grievor had applied for required a satisfactory drug and alcohol test and the Grievor informed the Employer of his cannabis prescription prior to testing.  When the results tested positive for THC, the Employer sought further medical information regarding the Grievor’s cannabis prescription. The Grievor’s prescribing physician provided information to the effect that while the Grievor should not drive for four hours after inhaling the cannabis, he could perform his day time job without impairment. Dissatisfied, the Employer sought further information.

While the Employer was awaiting the additional information, the Grievor sought to apply for another position which had been posted, that of an Assembler. When the Employer refused to consider him for the position while waiting for the additional medical information, the Union filed a grievance on behalf of the Grievor. The Union argued that the Grievor had the necessary qualifications and experience to perform the work for which he had applied and that the Employer’s refusal to accommodate and individually assess the Grievor’s ability to perform the work, was a failure to accommodate him and a violation of his human rights. The Union also pointed out that the Grievor had worked without issue for another employer on the Churchill project, while undergoing cannabis treatment.

The Employer argued that the positions that the Grievor had applied for were safety sensitive and that as part of the Employer’s legal obligation to ensure a safe workplace under occupational health and safety legislation, it had to determine whether the Grievor was able to work without impairment. The Employer stated that it had sought information to assess the Grievor’s situation on an individual basis but that the amount of information provided by the prescribing physician was limited. The Employer further argued that because there was no way to measure impairment from the Grievor’s use of cannabis as there was no test for measuring current impairment from cannabis, it increased the workplace safety risk and this amounted to undue hardship.


Based on the evidence, the Arbitrator found that the positions that the Grievor had applied for, were safety-sensitive. The Arbitrator also found that the Grievor had a disability, which required accommodation and that this accommodation had to be determined on the basis of an individualized assessment and in order to do this assessment, the Employer needed reasonable medical information.

Based on the expert testimony provided, the Arbitrator noted that THC can cause impairment, and that depending on the dose, the impairment could last up to 24 hours after last use because of the long half-life of THC. The Arbitrator further noted that as there currently is no test to accurately measure impairment arising from the regular use of cannabis, the use by the Grievor of medical cannabis was a legitimate safety concern in relation to safety sensitive positions and that under the Occupational Health and Safety Act regulation, workers are prohibited from being on a job site while their ability to perform work is impaired. Given these circumstances, it would be undue hardship for the Employer to permit the Grievor to work in the positions that he had applied for. At page 60, the Arbitrator stated, “if the Employer cannot measure impairment, it cannot manage risk”. The Arbitrator also noted that it would not be possible to address these issues through random testing, given the lack of ability to measure current impairment from THC use.

Employer Takeaways.

  • Accommodating an employee who uses medical cannabis in a safety sensitive position would amount to undue hardship as it poses an increased safety risk, which an employer cannot measure as there is no ability to measure current impairment from use of THC.
  • Accommodation of an employee using medical cannabis must be assessed on an individualized basis.
  • Random testing is not a solution, as there is no testing available to accurately measure current impairment of regular cannabis use.
  • Although it may amount to undue hardship to permit an employee who uses medical cannabis to work in a sensitive position, the employer’s duty to accommodate would require the employer to explore other options such as placing the employee in a non-safety sensitive position.