Fired Over a Failed Drug Test: What a June 2026 Ontario Ruling Says About Workplace Policies

Can your employer fire you "for cause" — with no notice and no severance — because you failed a workplace drug or alcohol test? A recent Ontario decision is a clear, plain-language example of when the answer is yes, and just as importantly, when it is not. If you work in a safety-sensitive job — driving, trades, warehousing, healthcare, heavy equipment — this is worth understanding.

The case in brief

In McCarthy v. Bison Transport Inc., 2026 ONSC 3729, released on June 25, 2026, the Ontario Superior Court of Justice considered whether an employer was justified in dismissing a worker for cause after a second positive drug test, in breach of the company's written drug and alcohol policy at a safety-sensitive workplace.

The court found that the employer had communicated the policy to its staff and enforced it consistently, and that breaching it a second time gave the employer just cause to end the employment. The wrongful dismissal claim was dismissed.

The court also addressed the worker's human rights argument. It found there was no disability or perceived disability in the circumstances and therefore no duty to accommodate under human rights law. As a backup analysis, the court noted that if the dismissal had been wrongful, it would have assessed roughly four months' notice, reduced by the worker's duty to look for comparable work (mitigation). It declined to award any aggravated or punitive damages, finding no bad-faith or unfair conduct in how the dismissal was handled.

Note: Bison Transport is a federally regulated trucking company, so parts of the case (including overtime claims) were decided under the Canada Labour Code rather than Ontario's Employment Standards Act. The human-rights and just-cause principles below, however, are relevant to workers across both systems.

Why "for cause" is a high bar — but not impossible

In Canadian law, termination for cause is the capital punishment of employment law. It means you can be let go immediately with no notice and no pay in lieu. Because the consequences are so severe, courts usually demand serious, well-proven misconduct. A single mistake rarely clears that bar.

What pushed this case over the line wasn't just the failed test — it was the combination of factors:

• A clear, written policy that employees knew about;
• Consistent enforcement (the rules weren't applied to one person and ignored

for others);

• A safety-sensitive setting where impairment creates real danger; and
• A repeat breach, not a first slip.

Take any one of those away and the result can change. An unwritten or inconsistently applied rule, a non-safety-sensitive role, or a first-time issue can all make a "for cause" firing much harder to defend.

The line between misconduct and disability

The most important takeaway for everyday workers is the difference between a disciplinary problem and a medical one.

• Recreational or casual use that breaks a clear, safety-based policy is treated

as misconduct. It can support discipline, up to and including dismissal.

• Addiction or a substance use disorder is generally a disability under

human rights law. Where a disability is genuinely in play, an employer normally must accommodate the worker — for example, through a treatment plan or a last-chance agreement — up to the point of undue hardship, before resorting to termination.

In McCarthy, the court found the facts did not establish a disability, so the duty to accommodate was not triggered. The lesson is not that addiction is unprotected — it is that the protection depends on the facts. If a disability exists and the employer is told (or ought to know), accommodation obligations can change the outcome dramatically.

Practical takeaways

For workers:

• Read the policy. Know the rules of your workplace, especially in

safety-sensitive roles. "I didn't know" is rarely a strong defence to a clear, communicated policy.

• If a health issue is involved, say so — appropriately. If you believe you have

a substance use disorder, getting that on the record (and seeking treatment) can engage the duty to accommodate. Employers can't accommodate what they don't know.

• Mitigate after a job loss. Even where a dismissal is challenged, courts expect

you to look for comparable work. Keep records of your job search.

For employers: a policy is only as strong as its communication and consistent enforcement. Apply rules evenly, document the steps, and treat a possible disability as a duty to inquire — not a reason to skip straight to firing.

Where to read more

• The decision: McCarthy v. Bison Transport Inc., 2026 ONSC 3729 on

CanLII.

• Workplace drug and alcohol testing rights:

Ontario Human Rights Commission.

• Federally regulated work and the

Canada Labour Code.

Get in touch

If you have been dismissed after a drug or alcohol test, or you are facing discipline and think a health condition may be involved, the deadlines move quickly. JSR Legals can help you understand whether your situation looks like misconduct, a wrongful dismissal, or a human rights issue — and what your options are. Reach us at info@jsrlegals.ca.

This article is general information about Ontario and Canadian law, current as of June 2026, and is not legal advice for any specific situation. Court decisions turn on their own facts — confirm how the law applies to you before acting.