PHOENIX - Arizona workers who use medical marijuana - should voters approve use of the drug in November - won't have to worry about being fired for testing positive at work.

A proposed initiative would allow doctor-authorized use of marijuana to relieve suffering from several specific conditions, and would allow creation of a network of nonprofit shops that could sell the drug.

The ballot measure also contains anti-discrimination provisions, including one that says an employer cannot make hiring, firing and disciplinary conditions based on a person's status as the holder of a medical marijuana card. That protection extends to someone who tests positive for the drug unless the company can prove the person used or possessed marijuana on the job or was "impaired" during work hours.

Andrew Myers, campaign manager for the Arizona initiative, said it is the intent of backers to prohibit workers from being fired for testing positive on the job.

"I believe that our language is very clear on that point," he said in response to the revelation a worker in Michigan was fired after testing positive. The man used marijuana under that state's law to deal with sinus cancer and a brain tumor.

But the Michigan law does not include the same worker protections contained in the version of the law likely to appear on the ballot here in November. Backers claim they already have the 153,365 valid signatures necessary to qualify.

Attorney Don Johnsen said current state and federal law does not require companies to make accommodations or provide special treatment for those who are using marijuana.

"This ballot initiative obviously would reverse that," he said.

Johnson said the provision allowing employers to terminate someone was "impaired" probably won't be much of a factor because "proving something like that is very expensive and very difficult and very risky."

Attorney David Selden said proving impairment will be difficult because, "Unlike alcohol testing, drug testing doesn't measure the current level of impairment."

Selden said it probably would take an employer catching someone smoking marijuana on the job, or possessing it, to be able to fire someone.

The initiative, modeled after similar laws in other states, requires "written certification" from a doctor to get up to 2.5 ounces of marijuana every two weeks. The drugs would come from nonprofit dispensaries.

Arizona voters actually approved a measure in 1996 allowing doctors to prescribe otherwise illegal drugs to seriously and terminally ill patients, only to have key provisions repealed by the Legislature.

That repeal was overridden by voters in 1998. But the wording of the measure - requiring an actual written prescription - made it useless after the U.S. Drug Enforcement Agency threatened to revoke all prescription-writing privileges of any doctor who wrote such an order.

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