Navigating Complexity: Medical Cannabis, the Workplace and Managing Risk


minutes reading time

DATE PUBLISHED: March 20, 2024

key takeaways

  • There is no definitive and agreed upon method to measure human impairment from cannabis containing delta 9 Tetrahydrocannabinol (THC) either in blood, oral fluid or by physical examination.
  • Regularly review and update your alcohol and other drug policies, recruitment, onboarding and testing procedures to take account of the evolution in the legal status of certain medicines and ensure management follow set procedures when issues arise.
  • It is important to understand the limitations of random drug testing from an evidence perspective.
  • Do not take employment law related actions relating to a medical condition and/or the use of prescription medication without: Robust supportive medical and other evidence to justify the actions being taken; and
    Considering anti-discrimination and unfair dismissal risks; and
    Taking legal advice

Navigating Complexity: Medical Cannabis, the Workplace and Managing Risk.

‘Cannabinoid Based Medicinal Products’ (CBMPs) or ‘medicinal cannabis’ (MC) are phrases used here interchangeably to describe: the use of medical cannabis (or cannabinoids, whether in plant ‘phyto’, endogenous, synthetic or isolated forms) as part of treatment for a specific symptom or disease.

From an evidence-based medicine perspective, medical cannabis may be indicated as beneficial in various medical conditions (including but not limited to chronic pain, epilepsy, sleep disorders, spasticity associated with multiple sclerosis, fibromyalgia, endometriosis, anxiety, depression and IBD). These are medical conditions that people in workplace environments regularly come across.

Why is this subject matter relevant in workplace settings?

To be an employer of choice in a tight labour market, how an organisation internally and outwardly projects their risk management approach to societal change associated with medical conditions and treatments, can impact how current and future staff view an organisation. People use prescribed medicines outside and/or during work hours which may impact their capacity to do the duties of their job if use causes impairment. Over 1 million legal medical cannabis scripts have now been issued in Australia since medical legalisation in November 2016 and over 5000 doctors have prescribed it.

Two ‘cannabinoids’ have been studied extensively which are prescribed and consumed widely in Australia amongst that cohort:

  • cannabidiol (CBD), which is non-intoxicating.
  • THC which is intoxicating (impairing) at certain doses.

Pain related conditions typically use THC containing products as that is in line with current international clinical practice guidelines for the use of CBMPs for chronic pain. However, whilst CBMPs containing THC may now be appropriate clinically for certain indications, the historical prohibition of cannabis has meant that the law in this area has not kept up with evolving medical advancements (e.g., driving with the mere presence of THC in bodily fluids, regardless of whether or not someone is intoxicated).

THC, Driving & Employment

Under s.79 of the Transport Operations (Road Use Management) Act 1995 (Qld), it is an offence to drive while under the influence of liquor or a drug, while s.79(2AA) deems it an offence to drive while a ‘relevant drug’ is merely present in blood or saliva (regardless of intoxication state).

A ‘relevant drug’ is a drug prescribed under regulation and under section 172 of the Traffic Regulation 1962 (Qld) includes THC.

Similar provisions exist in other Australian States and Territories except Tasmania which allows drivers to present a medical defence for driving with merely detectable levels of THC where the driver can show:

  • a medical script; and
  • the medication was taken in accordance with that script.

The implications of these limitations for employees and employers is that employees may be in breach of their employment contract, without the employee necessarily breaking the law. If an employee’s work duties include driving and they are taking medication that contains THC, it may render them incapable of performing their employment contract in its entirety. At common law, this may be grounds for contractual termination of the employment contract. However, employers must consider Federal and State statutory legal protections to ensure that there is not an inadvertent breach of other laws that govern the employment relationship (i.e., anti-discrimination and unfair dismissal laws).

Workplace Health and Safety

Under ss.31, 32, 34C and 34D of the Work Health and Safety Act 2011 (Qld) (WHS Act) there are risks of material fines/jail time where an employer fails in their health and safety duty, (including recklessly failing), if an employee/contractor is allowed/permitted to drive a vehicle or operate machinery whilst under the influence of THC (or any impairing drug) and an event occurs, where an employee/contractor is exposed to the risk of, or, actual death, injury or harm occurs.

Various civil and criminal penalties under the Act apply to both the employer entity and its directors and officers which can carry significant fines (up to $15.4M) and even imprisonment terms (up to 20 years)).

Critically, even where expert medical evidence is produced showing assessments undertaken determined THC impairment risk as low, these will likely be construed as merely assessing and quantifying risk and do not in any way result in a person being legally permitted to drive.

Driving while impaired from THC may also give rise to contributory negligence issues under Division 4 of the Workers’ Compensation and Rehabilitation Act 2003 (Qld). It may disentitle the claimant to compensation (s.305H(1)(e)) ‘If the worker relevantly was adversely affected by the intentional consumption of a substance that induces impairment’ and (per s.305(J)) there is a presumption of contributory negligence if the person who suffers injury is intoxicated.

Common Law Employer Liability Risk – THC and the Workplace

Employers have a duty to exercise reasonable care for the health and safety of employees in all circumstances and not to expose them to unnecessary risk of injury. They must provide a safe working environment as far as is reasonably practicable.

What is reasonable will depend on relevant facts of the matter and requires an assessment of potential risk of injury/harm that something may cause vs. cost to employer of implementing/changing safety protocols to mitigate risk.

Where a reasonable employer can foresee acts/outcomes that may cause harm, it would therefore be, a breach of duty of care (and would exposes them to liability) if no precautionary, or pre-emptive actions were taken when it had knowledge and power to do so.

Having an up to date, appropriate alcohol and other drug policy in place that is being followed procedurally by management assists in reducing risk of liability in negligence.

Anti-discrimination & Medical Cannabis

Under the Disability Discrimination Act 1992 (Cth) (DDA) and the Anti-Discrimination Act 1991 (Qld)  (ADA) it is unlawful to treat an employee/contractor less favourably due to a ‘disability’ (direct discrimination) or impose unreasonable requirements that cannot be complied with as compared to another person without the ‘disability’ (indirect discrimination).

It is unlikely that discrimination will arise if the ‘disability’ (under Cth law) or ‘impairment’ (State law) means the person cannot safely perform ‘inherent’ requirements of their job even with ‘reasonable adjustments’. Such ‘reasonable adjustment’ can be any adjustment UNLESS it imposes ‘unjustifiable hardship’ (which ultimately requires a weighing up of detriment/costs to the respective parties and context to the situation).

A further safeguard under the Fair Work Act 2009 (Cth) (FWA) affords workers protections from ‘adverse action’ in employment because of a ‘physical or mental disability’. The practical effect is that if action taken against an employee is lawful (and in accordance with the requirements under the DDA or ADA), it will unlikely to be ‘adverse action’ under s.351 FWA.

The implications of this are that: if an employee has a medical condition (i.e., that meets the definition threshold of ‘disability’ or ‘impairment’ under Commonwealth or State law), a Doctor prescribes medical cannabis, and the person responds well to the treatment, then allowing them to take their medical cannabis would be a reasonable adjustment. The corollary: prohibiting them from taking their MC would amount to discrimination unless it produces impairment and they cannot safely perform ‘inherent’ requirements of the job. In this regard, MC is no different to any other medication from an impairment perspective legally.

Unfair Dismissal & Medical Cannabis

There must be a ‘valid reason’ for an employment dismissal, which (in a medical cannabis context under current law) might include:

  • Driving duties are an inherent part of their job duties and cannot be conducted without breaking the law outlined above in the Transport Operations (Road Use Management) Act 1995 (QLD); and
  • No alternative role is available for which they are suitably qualified for by education, skill, and experience; and
  • No reasonable adjustment to their role can be made that would permit them to do it without breaching that Act
  • Driving (or working with heavy machinery) duties are an inherent part of a person’s job role and that cannot be safely performed (without impairment due to the presence of THC (with evidence of such presence)); and
  • No alternative role is available for which they are suitably qualified for by education, skill, and experience; and
  • No reasonable adjustment to their role can be made that would permit them to do it safely.
  • Non-disclosure of medical cannabis use in a job interview if specifically asked of their need to use a drug for a medical condition that would affect their ability to operate heavy machinery lawfully or drive a motor vehicle without being impaired.

What about if a medical condition and prescription arise after employment commences? Is there an ongoing duty of disclosure? This will depend on whether a workplace guideline is in place compelling them to do so is either directly or indirectly linked to a term or condition of employment and is enforceable. In these respects, an employer must be mindful of also following procedural fairness in any ‘show cause’ dismissal process for any defence to be ultimately upheld.

Medical Cannabis and Workers Compensation Claims – Learnings from NSW

There have been several recent cases in the New South Wales Personal Injury Commission where medical cannabis has been considered a form of medical treatment and has been deemed 'reasonably necessary' for injured workers, with cost reimbursement of medical cannabis allowed based on the specific circumstances of each case (predominantly for pain). The recent cases where the use of medical cannabis was accepted as a justifiable and necessary form of treatment under section 60 of the Workers Compensation Act 1987 (NSW) include:

  1. 1
    Van Den Hoek v Secretary, Dept of Communities and Justice [2023] NSWPIC 61
  2. 2
    Couch v Electus Distribution Pty Ltd  [2023] NSWPICPD 8
  3. 3
    Beatty v Johnston’s Transport Industries Pty Ltd [2023] NSWPIC 349
  4. 4
    Sehion v Maximum Energy Systems Pty Ltd [2022] NSWPIC 212
  5. 5
    Sheehan v Transdev Sydney Ferries Pty Ltd [2022] NSWPIC 422
  6. 6
    French v Harwood Slipway Pty Ltd & others [2022] NSWPIC 473
  7. 7
    O'Shea v Ramsey Food Packaging No 2 Pty Ltd [2021] NSWPIC 499
  8. 8
    Matthew Clark v Department of Transport [2020] NSWWCC 210
  9. 9
    Longworth v Secretary, Department of Transport [2020] NSWWCC 52

In contrast, Donnelly v Camsons Pty Ltd [2021] NSWWCC 19 ruled against the notion that medical cannabis was reasonably necessary in that particular case. It should be noted these are not Court decisions so are of limited precedential value. Nonetheless they are important as they show a trend of evidence-informed, health-related judgements on diagnosis, prognosis and effectiveness of cannabinoids as an intervention worthy of insurance reimbursement by a State government for medical injury at work.

In QLD, mental health related claims, WorkCover does not recognise the use of MC products in treatment and are therefore regarded as an ‘experimental intervention’ because ‘the current scientific evidence base supporting its efficacy and outcomes is limited’.  Accordingly, Employers with employees in QLD and other States and Territories will need to be aware of and adjust their insurance and policies and procedures to reflect the differences across the jurisdictions. 

So what? Why are these trends and stances of interest to employers? In order to minimise claims expenses (which, if rising, flow through to all payers of workers' compensation insurance premiums), novel interventions to reduce chronic pain to promote recovery, rehabilitation and return to work are worth paying attention to! On this, we have the longer term North American experience to look at where workers' compensation payouts declined in response to recreational cannabis laws adoption, both in terms of the propensity to receive benefits and benefit amount, with complementary declines in non-traumatic workplace injury rates and the incidence of work-limiting disabilities. Evidence that the primary driver of those reductions was an improvement in work capacity, likely due to access to an additional form of pain management therapy (cannabinoids).

Best Practice: Recruitment, Promotions, Drug Testing and the Privacy Act

The following can help mitigate challenges in organisations when it comes to cannabis (containing THC) and the workplace:


Declarations of medical conditions/ medications 

It is recommended employers expressly flag a positive obligation to disclose medical conditions/medications under applicable WHS legislation before and during employment. It is also critical to frame and actually treat such disclosures in a ‘reasonable adjustment’ context and NOT as a disqualifier for a role (given the discrimination law risks this gives rise to).


Promotions, Training Opportunities, Disciplinary Actions

Decisions should NOT take into account underlying medical conditions or medicine use UNLESS it is a material consideration that goes to the safety, fitness or performance in the role or training activity or conduct.



It is important employers treat medical conditions and treatment information disclosed to them as 100% sensitive information under the Privacy Act. It must be treated as confidential and securely stored (and deleted when out of date and not relied upon if not current).


Obtain Reliable Evidence

Treating doctor’s reports and/or independent medical examiner (e.g., Occupational Physician) reports are important evidential documents that can be used to make decisions. It is important to also understand the limitations of random drug testing. POCT for THC in oral fluid is increasingly used to detect driving under the influence of cannabis and in employment matters. POCT devices can be useful tools in detecting recent cannabis use; however, limitations should be noted from an evidence perspective as several studies have questioned the reliability and accuracy of two commonly used POCT devices based on time lapse from consumption point, and noting no definitive and agreed upon method to measure human impairment from cannabis containing THC exists.

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In QLD at present, the State Government has just concluded community consultations on potential reforms to cannabis and driving laws in QLD with a report due toward the end of 2024.

The influential RACQ have suggested a medical exemption defence be introduced into QLD law for the mere presence of THC in body fluids but retain offences for impaired driving (i.e., mirror Tasmanian Law).

If adopted it is reasonable to expect significant legal implications for:

  • Insurance (all types)
  • Mining, Construction, Driving and Heavy Transport sectors
  • Drug testing HR policies
  • Employment and anti-discrimination issues

Novel therapeutics (not just cannabinoids!) are an evolving area of the law. It’s important to be on the front foot on this subject matter but also to:

  • Stop, pause and reflect before taking employment law related actions that may be detrimental to your organisation or staff.

When you do need to take action, it's critical to have robust supportive medical evidence, full consideration of the anti-discrimination and unfair dismissal risks are undertaken and seek legal advice if in doubt about your position.


If you would like to discuss the implications of the content explained in this article, please contact Andrew Proudfoot of McInnes Wilson Lawyers for a discussion. Our market leading employment, workplace relations, commercial and health law practice areas are able to assist with the following and other issues:

  • Acting for organisations on issues of conjecture related to cannabis and other novel therapeutics (Workcover, Workplace Drug and Alcohol Policies and Checklists, Anti-discrimination policies, Workplace Health & Safety, and Insurance).
  • Dealing with other regulations/regulators relating to therapeutic goods and devices, such as TGA, ODC, AHPRA as well as ASIC (greenwashing), ACCC (misleading and deceptive conduct), ATO (R&D, corporate and personal income tax, GST), Commonwealth and State/Territory Health Departments.
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