In what context - are they travelling for work purposes or leisure?

Normally, the rules of that country would need to be followed regarding any medication/substances.

Hi Deborah
Would really need to know the particular manifestations and context / implications.
Many drugs etc - both legitimate and illicit - affect behaviour and capability and perhaps safety at work and if this is the problem, it's probably not too relevant to an employer whether and exactly where they were medicinally prescribed - save for maybe making any possible reasonable workplace adjustments. But if the cannabis is simply showing up on eg random drug and alcohol testing in the absence of any other of the former concerns, then the 'medicinal use' context might be a mitigating or even exempting factor, depending of course on professional medical advice and guidance.

I am just thinking out loud here, prescriptions for medical cannabis must be issued by a UK doctor and filled by a UK registered pharmacy. UK pharmacies cannot accept prescriptions from abroad.Is the employee importing cannabis into the UK via mail or in person? Unless they have a personal import licence which i doubt! I would first advise the employee to arrange a consultation with a UK based specialist such as Releaf and Curaleaf to ensure that their medication is legally prescribed and the employee is issued with a Cancard ID. How did you become aware that the employee is using medical cannabis? Is the medication affecting their job performance or workplace safety? If so i would deal with this situation the same way i would deal any case where an employee's job is affected by medication.