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

https://star-wiki.win/index.php/The_Motorist%E2%80%99s_Guide_to_Medical_Cannabis:_DVLA_Rules,_Section_5A,_and_Staying_Legal

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