In the US, employers have the legal right to drug test workers. The rationale seems reasonable enough; employers should be able to require workers to be sober on the job. Yet while they claim to be concerned about impairment, drug testing pursues something else entirely.

Employers do not to screen for prescription drugs such as OxyContin.

“Right now it’s one of the most abused prescription drugs,” says one DEA official. “It’s certainly the most dangerous.”

Still… employees with chronic pain, and people who just like to get high, can ‘Rush’ through their day on Oxy with no risk of losing their job because of a failed drug test. They cannot choose marijuana.

When body chemistry is what is tested (instead of impairment), a person’s choice of medication becomes an issue even when their behavior is not. And that is exactly what has been happening to medical marijuana patients in some states.

Marijuana is an odd substance when it comes to drug screening. Unlike most drugs, marijuana is not water-soluble. This means that marijuana metabolites remain in the user’s body for a very long time. For example, marijuana users can test positive over a month after they have smoked marijuana, while a cocaine user almost immediately tests “clean.” This leaves medical marijuana patients extremely vulnerable.

In response, lawmakers in Oregon are considering two bills to address the issue. One bill would protect cannabis patients from being fired merely for their choice of medication. Another bill, which was introduced a few weeks ago, would allow employers to punish any employee who tested positive for marijuana, even if that person is a legitimate, registered medical patient.

If Legislators choose to enact the more restrictive bill, employers will be able to dictate to employees what legal medications they can buy and consume when they are ill.

Hopefully, Oregon will instead recognize that the persistence of marijuana metabolites in the body should never be allowed as the sole cause for termination. The medication that a person took last month has no bearing whatsoever on that person’s ability to perform their job today.

Workplace drug testing is designed primarily to see if you smoke marijuana. That is why if Oregon’s Legislature sides with the rights of sick people, the consequence might be interesting. If medical marijuana patients receive the rights they deserve as Americans, workplace drug testing is liable to stop altogether in Oregon. Sorting the patients from the recreational users would put HR in a tough spot, and company’s are simply not going to be willing to spend money to run down the senior execs who blow coke lines at work.

But until the Legislature acts, sick people will continue to suffer.

“The bottom line is I need a job and I don’t make enough through social security and food stamps,” said Judy Adamson, a 61-year-old widow, breast cancer survivor and registered medical marijuana user. Adamson was suspended from her job after her former employer ordered her to take a drug test.

Sick people shouldn’t have to ask their boss what medicine they can take. We’ll see what Oregon has to say.

To read more on the issue, check out Business Week’s article.