Hello again smokinnurse. I posted in your other thread - please read what I wrote there and I hope it helps.
I have had this issue come up before for my mother - not for employment but for her pain doctor.
We live in a state without medical or recreational legalization, and my mother very rarely smokes although she does prefer it. She has been disabled for 14 years from a head bleed and stroke and has taken fairly heavy opiates for pain control the entire time since... Prior to her stroke she was a light and occasional drinker, and occasionally smoked with old friends on social occasions (although I did not know that when I was younger). Her doctors were the ones who started her on the opiates, and over the past 14 years the laws and restrictions on prescription pain killers and chronic pain sufferers have gotten almost absurd - especially in our state.
To make a long story short, not too long ago at my mother's usual 3 month visit to her long-established pain doctor she decided to make her take a drug screen for the first time ever. Not expecting this my mother had to produce a urine sample to be able to get her pain medications. I don't think she honestly thought it was going to be a problem. The next week she received a call explaining that she had tested positive for marijuana, and the put her in a 'probationary status'. They would allow her next 30 day supply of medication, but she would need to meet with a clinical psychologist in that time period to evaluate her, and right before her prescriptions would run out they scheduled her to see her pain doctor again - at which time she would have to test negative for everything but her pain medication or she would be dismissed from the practice...
It turns out one of my mother's oldest friends had given her a small amount of pot a week or two before the doctors appointment. I'm sure my mom stretched that herb as far as it could go because it was a rarity for her and she didn't need much. She didn't think anything of it because she had never been drug tested by her doctor. After she learned this I found out about it. My very first thought was "Tell them you went and saw your cousin in Colorado for a week not long before the appointment." My mother does have a cousin who lives outside of Denver, and I figured what the hell - it's legal in CO now!
Again I'm trying to keep it short as possible. That story worked for my mother's purposes, although wouldn't look so good on a pre-employment drug screen. My mom told that to the psychologist (who probably only had her in his office for like 10 minutes) - he made no further recommendations. She also told her pain doctor the same at the next appointment, who lectured her for a few minutes on the changing laws and her responsibility as a doctor to keep my mom on the prescribed medication plan - which did not include other non-prescribed medications (yes she referred to marijuana as a medication). They then conducted the follow-up drug screen, and my mother passed. There have been no issues since.
So anyway, using the Colorado excuse may work in situations like these. However when it comes to employment you will not get the job. Even in Colorado and Washington it seems to be up to the employer's discretion how they choose to interpret the new state laws in regards to new-hires. In the healthcare industry you can almost certainly guarantee that no employer will hire anyone who tests positive for marijuana, even in CO and WA. Same with the medical states. In my state the large hospital systems have even stopped hiring "tobacco" users (which means nicotine) which is really just a ploy to keep their health insurance premiums down... I have managed to quit smoking cigarettes in the last months thanks to vaping - but I still use a nicotine product... That needs to go to the Supreme Court in my opinion if they can't discriminate based on gender, race, religion, sexual orientation, age, etc. but CAN discriminate against smokers/vapers while they sit there sipping their coffee??? But enough ranting about that... I'm just trying to point out how the healthcare industry is one of the MOST restrictive when it comes to pre-employment "screens"...
