One of the U.S. legal rights on taking tests for illegal drugs or the use of alcohol while driving, flying, working or any other reason to test is protected unless the person asking(law enforcement, employer or a private citizen, has to have probable cause before acting .
Oregon made the use of Cannabis legal for recreational use, STUPID!
One of the last drug training seminars I attended in 1996 brought up the length of alcohol, morphine, heroin and many other water soluble drugs affecting the human brain, which was 72 hours after the last consumption.
THC remains in the fatty tissue in the human brain affecting it for up to six months after the last use One of the other points brought about THC is it will build up in your system and increase its affect on the brain the more you consume it, hence the name "Pot Head"
Most mind affecting drugs are depressants that slow down your brains ability to think and reaction times, NOT GOOD
I've seen several racers at the races park their rigs a long ways down wind from other racers and then later smelled the skunk weed in use near them years ago before weed was legal any where
The bright side of that was I could out drive them easier when they were under the influence than when they where sober