Here’s the sad reality of last week’s court decision upholding the termination of an employee in Colorado who lost his job because a random drug test turned up medical marijuana in his system: Even if your state decides that marijuana is legal, the ongoing federal prohibition still trumps all.

Keith Stroup, NORML’s Legal Counsel, made this very point in a recent commentary that cut to the heart of the problem:

This case highlights one of the most pressing issues that needs to be addressed in the states that have legalized medical cannabis use — and the states that have adopted full legalization for all adults, as well. Although employees are protected from arrest and prosecution under state law by these various laws, they remain vulnerable to employment discrimination in almost all states.

Simply put, if an employer wants to insist on what they frequently call a “drug-free workplace,” they are legally permitted to do that — regardless of the unfairness this policy may cause, because we must note that they do not apply those same standards to off-job alcohol consumption or the use of prescription drugs.

Most Americans would strongly support the right of an employer to fire anyone who comes to work in an impaired condition. But smoking marijuana leaves one mildly impaired only for about an hour and a half; certainly smoking marijuana in the evening, or on the weekend, would have no impact on the employee who comes to work the following day.”

Amen to that, I say, because most everyone I heard from seemed stunned by how the Colorado State Supreme Court ruled in this case. They seemed to believe, as I do, that the issue is impairment on the job.

How many times have you talked to a fellow worker and they said something like, “I’m really having a hard time today because the doctor has me on xxxx for xxxx, and it really knocked me out.” To me, THAT’s someone who is impaired on the job, not someone who ingested a little medical marijuana last night, at home, for a medical condition.

Even Fortune magazine — not exactly a bastion of the cannabis culture — questioned the logic of the court ruling in an article titled How the Colorado Supreme Court Just Confused Every Employer in America.

It’s point: While this ruling may be a problem for larger employers who have to worry about the big foot of the Feds stomping on them over federal drug laws, small employers may be able to fly under the radar — in state’s where cannabis is legal.

As Fortune put it:

Smaller companies … may be willing to be more flexible because they attract less public scrutiny. Also, due to the higher relative costs of replacing employees, smaller businesses might be more willing to implement management policies that account for off-duty use of medical marijuana while also factoring in whether it affects an employee’s job performance or whether the business could reasonably accommodate the employee’s use.”

But, it also went on to say this:

Whether efforts like these adequately and appropriately address the very real and sometimes conflicting concerns for employers about employee retention and drug use remains an open question. But one thing is certain: employers will have to decide what to do on a piecemeal basis and with little guidance from the law.”

Yes, employers WILL have to decide what to do on their own, without much (if any) specific guidance from the law.

That’s a sobering fact for businesses everywhere, and yet another reason why the federal government’s inability to deal with state legalization of marijuana is getting to be a bigger problem the longer the Feds sit back and twiddle their thumbs.