High stakes: Navigating medicinal cannabis in the workplace

09 November 2023

Dealing with cannabis used to be simple for employers – if an employee tested positive then they could be disciplined or dismissed. It’s not that easy anymore!

Australia legalised the use of medicinal cannabis in 2016. Since then, we have seen an increasing number of employees being prescribed medicinal cannabis for chronic conditions, anxiety, back pain and managing the ongoing side effects of chemotherapy treatment. This has created an enormous challenge for many of our clients, especially in the resources industry, who now need to balance work health and safety obligations with anti-discrimination legislation.

The challenges for employers

With the introduction of the Work Health and Safety Act 2020 (WA) and the increased penalties for contraventions, employers must be alert to safety issues in the workplace more than ever before.

Unlike other prescribed and over the counter drugs that can cause impairment, there is no reliable evidence yet about the impairing effects of the available forms of medicinal cannabis. This means that there is no evidence available to employers which establishes the length of time the impairing effects of medical cannabis may last and whether employees can perform work safely or make good decisions with medicinal cannabis in their system.

Unfortunately, the effects of medicinal cannabis, as opposed to illicit cannabis, on an individual are yet to be significantly researched. Further unknown factors include the long-term effects of medicinal cannabis or how medicinal cannabis interacts with other prescription drugs.

In addition, there is no objective test for impairment which can easily be administered at a worksite. Employers have routinely relied on testing for the presence of impairing drugs, including cannabis. As cannabis is metabolised differently from other drugs of impairment, an employee can return a positive test result for the presence of Tetrahydrocannabinol (THC) and/or cannabidiol (CBD) long after the drug was taken.

It doesn’t help that most medicinal cannabis products in Australia are not approved by the Therapeutic Goods Administration (TGA) for safety, quality or effectiveness.1 In the absence of TGA regulation, there is no verification process for the potency of the product or its purity. This means that a product marketed as CBD-only may, in fact, contain THC. There is clear evidence that THC causes impairment, but it is less clear whether CBD is impairing.

Another challenge is that because medicinal cannabis is not regulated there is no standard dose given to patients. The amount of medicinal cannabis an employee ingests could be inconsistent from the amount recommended by their doctor, which may result in impairment. It is also not possible for a drug test to differentiate between medicinal cannabis and illicit cannabis.

No jurisdiction in Australia has any guidance from the regulators as yet as to how to manage medicinal cannabis in the workplace.

Employee claims

Both state and federal equal opportunity laws and the Fair Work Act 2009 provide employees with some protection from adverse action, or discrimination, for taking prescribed medicinal cannabis. In effect these laws make it unlawful to discriminate against a person on the basis they have a disability. ‘Disability’ is broadly defined to include the physical and mental impairment of a person.

Importantly, none of these laws allow for lawful discrimination because the employer is complying with a work health and safety duty.

If an employee discloses that they are taking prescribed medicinal cannabis, employers should seek advice before taking any ‘adverse action’ against the employee (such as suspending or dismissing them) to minimise the risk that the employee could make a general protections or discrimination claim.

In addition, while an employee returning a positive drug test for THC and/or CBD may be a valid reason for dismissal, their dismissal may still be harsh, unjust or unreasonable in the circumstances.

Case Law

Most of the cases to date dealing with medicinal cannabis have been unfair dismissal cases. As far as we are aware, no jurisdiction in Australia has had a final decision in relation to a discrimination claim on the basis of medicinal cannabis as yet.

In Sheldon Haigh v Platinum Blasting Services Pty Ltd [2023] FWC 2465, the Commission upheld the dismissal of Mr Haigh from a ‘safety critical’ role, after he failed to update his employer about changes to his medical regime, including the taking of medicinal cannabis, which was a breach of the employer’s policies and procedures and his employment contract. The Commission in this case noted that even though it appeared that Mr Haigh took measures to ensure that he was not impaired before working on site, the use of medicinal cannabis ‘did have a possibility of impairment‘.

On the other hand, in the earlier case of Sydney Trains v Gary Hilder [2020] FWCFB 1373, the Commission found that an employee was unfairly dismissed for breaching a Drug and Alcohol policy and Code of Conduct, as the employer’s ‘zero tolerance approach’ to medicinal cannabis was inconsistent with its disciplinary policies, which required mitigating circumstances to be considered.

We expect to see more judicial consideration of medicinal cannabis and the workplace, that will provide guidance for how employers can manage this complex issue.

In the future

Medicinal cannabis is unlikely to be the end of this challenge for employers as three new drugs of impairment are being increasingly prescribed. These are MDMA, psilocybin and ketamine. MDMA and psilocybin are being prescribed to treat post-traumatic stress disorder and Ketamine is now being used to treat depression. At present, the use of these drugs is highly controlled but if trials are successful, we may see more employees being prescribed these drugs and expecting to be allowed to attend work. Employers will then need to consider how these drugs are to be managed within their drug and alcohol policies and procedures.


Employers should:

  • consider developing or updating their drug and alcohol policies and procedures to include medicinal cannabis;
  • use a risk assessment procedure to address concerns of the impact of medicinal cannabis on an employee’s fitness for work;
  • implement/update their processes for carrying out drug testing;
  • adopt a consistent approach as to how they manage other drugs and risks (such as fatigue) which may impact on the way employees safely carry out their duties; and
  • stay up to date with new evidence relation to the impairment of an employee taking medicinal cannabis and testing methods.

Our team can assist with reviewing your policies and procedures, or providing advice on managing medicinal cannabis and how to mitigate the risk of legal claims by employees.

This article was written by Zoe Weir, Partner, Rochelle Airey, Special Counsel, Audrey Ooi, Lawyer and Jackie Sorial, Law Clerk.

1 Australian Government Department of Health and Aged Care, ‘Guidance for the use of medicinal cannabis in Australia: Patient information’ Version 1 December 2017 Guidance for the use of medicinal cannabis in Australia: Patient information | Therapeutic Goods Administration (TGA).

Zoe Weir

Partner | Perth

Rochelle Airey

Special Counsel | Perth

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