They are arguing this because it is true. The tests in use can read positive for weeks or months after last use.
They need a test for the active ingredients rather than metabolites of THC.
Even Iceberg Slim wrote in his autobiography PIMP that he didn't want his hookers smoking pot because it made them to lazy to go to work.
You can drink alcohol and still have your performance affected the next day.
If the goal is to prosecute those who are IMPAIRED and the measure is blood/breath (not performance), then pot smokers can go screw because they haven't argued this standard for all DWI/DUI prosecutions. Same as how they don't care that tobacco smokers can be denied employment and how they've long demonized tobacco and alcohol as bad for the body while pot is “natural”.
Get off how ever you want but demonizing the norms of society only slits your own throat.
Funny to see the FDA now limiting the use of caffeine. Ever drink a cup of “police officer coffee” that's been laced with NODOZ for while they file paperwork at late night diners?