The California Supreme Court ruled 5-2 Thursday that an employer could fire an employee who use medical marihuana at home and test positive at work even though his doctor prescribed the substance.

According to the ruling, Proposition 215, also known as the Compassionate Use Act, which allow patients to legally use marijuana for medical reasons and which protects caregivers who prescribe the drugs to their patients, did not protect any worker from possible professional repercussions that may come from using the doctor-recommended drug.

The ruling comes in a lawsuit filed in 2002 by Sacramento attorney Stewart Katz on behalf of Gary Ross, a former systems administrator at RagingWire Telecommunications who suffers from chronic lower back pain and muscle spasms. As Ross’ trial to cure his condition with muscle relaxants and traditional pain medication failed, his doctor prescribed him marijuana. Although Ross was a qualified patient under the Preposition 215, approved by voters in 1996, he was fired from his job in 2001 after he had tested positive for the substance.

Mr. Ross filed suit, sustaining that his dismissal violated state laws barring wrongful termination and discrimination based on disability. However, the Court rejected that argument on Thursday, saying that the act deals solely with criminal prosecution, not term of employment.

“What are they supposed to do? Employers are held liable all the time when drunk or stoned employees cause trouble, either in the workplace or driving home. That's one of the reasons why the drug-free workplace is so important,” said Deborah La Fetra of the Pacific Legal Foundation, which filed a brief supporting the company, according to the Washington Post.

Advocates of medical marijuana said Thursday that they hoped the Legislature would offer workplace protection to medical marijuana users. Assemblyman Mark Leno, a Democrat from San Francisco, said he planned to take up the cause.

The ruling “strikes a serious blow to patients’ rights,” he said, according to the Associated Press.

“We remain hopeful that the legislature will come to the aid of patients by preventing the sort of discrimination that is likely to occur from such a decision,” Joe Elford, chief counsel of Americans for Safe Access who represents Ross said, according to the same source.

The advocacy group estimates that 300,000 Americans use medical marijuana.

Eleven states have adopted medical-marijuana laws similar to California’s: Alaska, Colorado, Hawaii, Maine, Montana, Nevada, New Mexico, Oregon, Rhode Island, Vermont and Washington.