For EV owners using prescribed medical cannabis, a statutory defence exists,...

https://evpowered.co.uk/feature/medical-cannabis-and-uk-driving-laws-what-ev-owners-must-know/

For EV owners using prescribed medical cannabis, a statutory defence exists, but it’s not a free pass. You must stay under the 2mcg/L THC limit, remain fit to drive, and inform the DVLA. Remember: legality never replaces your personal responsibility.