Recent studies have proven that regular use of caffeine and subsequent omission or withdrawal results in drowsiness and inattention - (due to changes in the brain to increase the number of sleepiness indicators to offset caffeine's effect).
Many drugs warn not to drive or operate machinery if they cause drowsiness. It seems arguable that caffeine has an obviously delayed effect but still ultimately causes drowsiness (and it's also more than a natural level of drowsiness because of side effects of caffeine use).
How does caffeine escape this regulation and the consequences of it? (e.g. if someone crashes car after forgetting their regular coffee earlier in day, who is liable?)