Not while they are on the job. But if the night before they wanted to I would be all for it.
God, you're stupid.
A BAC test can determine WHEN alcohol was consumed based on the level in the blood stream. Metabolisms vary, but in general, you can tell if a person has a BAC of a certain level, they had to have consumed X amount of alcohol at least Y minutes or hours ago.
HCL is different. The only way to measure intoxication from HCL is a sobriety test, which is only a blunt gauge of whether someone is impaired, not by how much.
HCL can remain in the system, hair, scalp, etc, for days after recreational use, and weeks to months for habitual users. Trying to hold pot smokers to the same standards to determine degree and time of intoxication is pointless. The only sure method of keeping people from being high on the job is a zero tolerance drug screen for HCL. Don't like it? YOU HAVE THE FREEDOM TO FIND ANOTHER PLACE TO WORK.

(Sound familiar?)
Anyone can appear to be a little lightheaded and not be intoxicated -- not quite awake yet, stood up too quickly, or any number of quick motions that made them temporarily dizzy. What's the standard to know if a pilot just lost his balance for a second vs. still buzzing from morning joint?
You can say all you want about "this is okay, but that isn't", but without standards to identify violators and enforce the rules, the risk outweighs all other benefits of "he said he was okay to fly, and I have to take him at his word."