Washington State should have seen it coming. After all, pot growers and pot dealers were two of the loudest factions trying to kill California's Prop. 19 last fall. They didn't want voters to decriminalize pot, didn't want any disruption to their business model, just didn't want change. The measure failed, narrowly. So in this new political landscape where marijuana legalization looks increasingly within reach, it's par for the course that the people currently opposing Washington's legalization measure, Initiative 502, are the biggest pot smokers of all: medical marijuana patients.

Not all of them, of course. But enough that they've launched a polished website called Patients Against I-502, started an aggressive Facebook campaign designed to peel away votes, and issued statements publicly opposing the initiative.

Filed in June, I-502 is sponsored by prosecutors (including former US Attorney John McKay) and public-health leaders, and is widely seen as the most cogent, competent effort in US history to legalize, tax, and regulate marijuana. It appears headed to the 2012 ballot, with nearly a million dollars pledged and over 100,000 signatures collected. Two credible polling firms have found this year that about 54 percent of state voters support the measure.

"Washington has a chance here to displace California as the primary vehicle for reforming marijuana laws," says Allen St. Pierre, director of the National Organization for the Reform of Marijuana Laws, on a phone call from K Street in Washington, DC.

I-502 would still allow authorized patients to grow, use, and exchange pot under the existing medical-marijuana law passed by voters in 1998. But certain medical pot activists are complaining that I-502 wouldn't allow people to grow pot at home (only buy it in stores), and that it only allows adults to buy and possess one ounce of pot (patients could still have up to 24 ounces, but they say the one-ounce limit is too restrictive for recreational users). They also say that a DUI provision is so toxic that the entire measure should be rejected.

Edward Agazarm, one of the most outspoken promoters of the anti-502 website, sent an e-mail this month with a subject line declaring that the initiative amounts to "rape by cops w/guns and the ACLU."

What does he mean by "rape"?

The "rape"—according to Agazarm, who is also vice president of the Citizen Solutions firm that petitions for Tim Eyman initiatives—is that I-502 sets an automatic cutoff for stoned driving. Anyone with 5 nanograms of THC per milliliter of blood would automatically be guilty of a gross misdemeanor. "That level is NOT supported by science and would subject patients to highly invasive blood testing, unnecessary confinement, and a criminal conviction that will haunt them for life," the activists' website says. For essentially these same reasons, prominent medical-marijuana patients Ric Smith and Vivian McPeak, director of Seattle Hempfest, have opposed the measure. Medical-marijuana attorney Douglas Hiatt has also denounced I-502.

They're right that the science is minimal and some people could exceed the 5-nanogram limit, if they are regular medical-marijuana users, without necessarily being impaired. They note that even Washington's blood-alcohol limit of 0.08 percent is still debatable in court, whereas this measure would result in an automatic conviction for exceeding the THC limit.

But several attorneys say that marijuana DUI arrests wouldn't increase.

"The concern is not warranted," says Seattle City Attorney Pete Holmes, a prosecutor and co-sponsor of the initiative. He says that even in the 11 states that allow medical marijuana but have zero tolerance for THC, "they haven't seen an increase in the DUI prosecutions for marijuana."

Alex Newhouse, a criminal defense attorney in Yakima, points out that if voters pass I-502, officers would still need probable cause to stop a car and would need to find evidence of driver impairment before seeking a blood draw. Even then, he says, any tests would have to be conducted by a medical professional (typically at a medical clinic or an ER). "If a person is not driving erratically and they don't appear intoxicated, [and] there is nothing for the officer to see in plain view, there is no probable cause to investigate anything," Newhouse says.

And I-502 arguably does something useful for marijuana users accused of a DUI. It separates active metabolites, which indicate inebriation, from THC-COOH, the inactive metabolite that remains in the system for days or weeks. In other words, it tests to see whether people have used marijuana recently, not simply whether they've used marijuana in the past month.

Why include the DUI language and the provision about only purchasing pot in licensed stores? So the initiative will pass. That's what New Approach Washington's polling showed would win (54 percent to 38 percent). That DUI provision alone prompted 62 percent of voters to say they were more likely to support I-502, and only 11 percent said it would make them less likely to support the initiative, according to a poll in May by Quinlan Rosner Research.

"Nobody likes people driving a two-ton piece of metal on the public highway while they are impaired and putting people at risk of death or serious injury," explained Alison Holcomb, New Approach Washington campaign director. "That is not acceptable in our society."

The sponsors of Patients Against I-502 did not reply to an e-mail seeking comment. recommended