PORTLAND (AP) — An employer is not required to accommodate the use of medical marijuana, the Oregon Supreme Court ruled in a case that cost a worker his job, saying state law is trumped by US federal law that classifies pot as an illegal drug.

A legal expert called the divided 5-2 ruling "a shot across the bow" of those who support medical marijuana or legalising grass altogether.

The court overturned a state Bureau of Labor and Industries decision in favor of a worker in Eugene who was fired after telling his boss he was using medical marijuana approved by his doctor before taking a drug test.

Anthony Scevers filed a discrimination claim against Emerald Steel Fabricators Inc., arguing the company failed to make a reasonable accommodation for a disability.

But the majority, in an opinion by Justice Rives Kistler, supported the company's argument that "state law does not require an employer to accommodate an employee's use of marijuana to treat a disabling medical condition." It added that "the federal Controlled Substances Act prohibits the possession of marijuana without regard to whether it is used for medicinal purposes."

The ruling was praised by Associated Oregon Industries, the state's largest business lobby, which wrote a friend of the court brief supporting Emerald Steel.

"The decision now means that employers can be assured that they can consistently enforce their zero-tolerance drug policies," AOI said in a statement.

But Brad Avakian, chief of the state Bureau of Labor and Industries, said the ruling "seriously undercuts" the Oregon medical marijuana program approved by voters in 1998.

"The immediate impact of the Supreme Court's decision is to remove the employment protection that medical marijuana users had under Oregon's disability law," Avakian said.

The court majority noted that its ruling did not affect the way Oregon law protects medical marijuana from any state criminal liability.

Even though marijuana is illegal under federal law, US Attorney General Eric Holder announced last year the Obama administration would relax prosecution guidelines for medical marijuana.