Medical marijuana laws are designed to ease pain for migraine sufferers and other people with conditions that leave them in chronic pain. Now they are also causing headaches for employers.

Luke Vezey, a Colorado Springs man with a medical marijuana card state law requires to light up legally, was fired from his job for failing a drug test.

Vezey, who suffers from chronic stomach pain, told Colorado's KKTV Thursday: "What I do is strictly for my stomach. I do it out of work, I've never come in under the influence."

He worked as a guard at a private-jail facility which has a zero-tolerance drugs policy he says he was aware of when he was asked to take a random drug test. He failed the test, was placed on leave, and then received a certified letter firing him.

Vezey has hired a lawyer to fight the decision, but Colorado Springs lawyer Kevin Donavon (who is not involved with the case) says the law is confusing.

"There is no prescription, marijuana prescription. It's a recommendation by the doctor and if you have that recommendation that allows you immunity from prosecution," Donavan said. But nothing in the law prevents a user from losing his o her job after a positive drug test. Vezey's former employer declined to comment, citing privacy reasons.

Last month, New Jersey became the 14th state to make marijuana legal for medicinal purposes, and an additional 12 states have pending legislation – meaning more and more employers will find themselves considering adding a Marijuana FAQ to the employee handbook. Only Rhode Island specifically protects workers from being fired for their medical use of the drug.

Taken on doctor's recommendation or not, pot use remains illegal under the federal Controlled Substances Act. But in October the Department of Justice announced that federal agents will target users and distributors only when they violate both federal and state laws.

Where does that leave employers? It's all uncertain legal ground.

Consider California, where in 2008 the state Supreme Court ruled 5-2 in favor of computer data storage company RagingWire Telecommunications (No. 1700 on Inc's 2009 5000), which fired a systems engineer--a disabled veteran who lit up to ease his chronic back pain--for failing a drug test.

The court said that Proposition 215, which allows use of marijuana for medical purposes with a doctor's recommendation, does not protect workers for being fired for violating federal drug laws before, during, or after work hours.

What's more, an employer who knowingly hires a medical marijuana user is "arguably complicit in an activity that's illegal under federal law."

Montana also has upheld an employer that fired a worker who failed company drug tests, but each state law is different and the issues haven't been fully tested in the courts. In Montana's FAQ for medical marijuana users, the answer to "What should I tell my employer if I am subject to a drug test?" is "The law is silent on this issue."

Then there's Michigan, where the law says a registered user can't be "subject to arrest, prosecution or penalty in any manner or denied any right or privilege including... disciplinary action by a business." But another part of the law says "nothing in this act shall be construed to require an employer to accommodate the ingestion of marijuana in any workplace or any employee working while under the influence of marijuana."

It gets even hazier when you consider the Americans With Disabilities Act, under which an employee fired for using pot for health reasons could in theory pursue a lawsuit claiming discrimination. Is pot-use, for example, a reasonable accommodation you need to grant an employee in chronic pain? Or, if an employer has a zero-tolerance policy for drug use, would creating an exception for medical marijuana users create another kind of legal exposure? And what about employees who operate heavy industrial equipment or have other job responsibilities where workplace safety standards come into play?

Advocacy group Americans for Safe Access already has reported hundreds of complaints of discrimination by employers. "It's a gray area to know what you can do," Danielle Urban of employment law firm Fisher & Phillips told the National Law Journal. "But I think it's still risky to just fire someone for using [marijuana.]"