Medical cannabis users must be careful. While a defence exists for the 2µg/L...

https://research-wiki.win/index.php/Do_I_have_to_tell_the_DVLA_about_prescribed_medical_cannabis%3F_A_guide_for_the_cautious_driver

Medical cannabis users must be careful. While a defence exists for the 2µg/L THC limit, you must still meet DVLA fitness standards. Legality isn't a safety pass: if your prescription impairs you, don’t drive