Considering the haziness surrounding medical marijuana laws, it may be surprising that some of the most uptight places in the Bay Area — local airports — are also some of the most laid back when it comes to medical pot patients.

San Francisco police, who patrol San Francisco International Airport, say they allow card-holding medical marijuana patients to carry up to 8 ounces of dried cannabis when traveling. The SFO policy follows the guidelines police use within the city of San Francisco, said Sgt. Wilfred Williams.

Then-San Francisco police Chief Heather Fong enacted the policy in November 2008 through a three-page bulletin to officers. It instructs officers to leave medical marijuana patients and their drugs alone if they are using the marijuana for medical purposes and not for criminal activity.

And when it comes to air travel, local police — not airport officials or federal authorities — determine which passengers can fly with medical pot.

Transportation Security Administration spokeswoman Suzanne Trevino said airport security officers are trained to check for dangerous items such as explosives when screening departing passengers, their carry-on bags and checked luggage.

TSA officers sometimes find items such as drugs and child pornography, however, and turn them over to local law enforcement, which decides what to do with the items and the passenger, Trevino said. If the local police force allows the passenger to keep their medical marijuana, the TSA would not stop them from traveling with the drug, she said.

Likewise, SFO spokesman Mike McCarron said officials at the transportation hub have nothing to do with enforcement of medical marijuana laws at the airport.

At Mineta San Jose International Airport, enforcement of medical marijuana laws is left to San Jose police, said airport spokesman David Vossbrink.

San Jose police Sgt. Ronnie Lopez said they also do not arrest or cite passengers with medical marijuana at the airport or seize their drugs. They do, however, write a report and send it to federal authorities, who determine whether to file charges, he said.

In years past, that may have posed a problem to medical marijuana travelers, but the Justice Department this week told its U.S. attorneys to back off prosecuting medical marijuana users who comply with state law.

In the East Bay, the Alameda County Sherriff's Office enacted a specific policy last year that allows medical marijuana users to travel from Oakland International Airport with the drug. As at SFO, a qualified patient or primary caregiver as defined by California law can carry up to 8 ounces during travel out of Oakland.

Of course, just because passengers are allowed to take their marijuana out of the Bay Area does not give them full immunity from prosecution, as more than 30 states ban medical marijuana. If a Bay Area traveler lands in a place where the drug is illegal, they could be prosecuted by state authorities.

Alameda County deputies notify passengers flying out of Oakland that they could be violating the law if they land in one of the many states that ban medical marijuana. But they have never called ahead to notify police on the other end.

Despite the policies, many patients are hesitant to travel out of local airports with their medical marijuana, said Nathan Sands, vice president of the Compassionate Coalition, a Fairfield-based nonprofit medical pot advocacy group. Airports have gained a reputation, particularly following the Sept. 11 attacks, for confiscating normally legal items, such as liquids, at TSA security gates.

"I think a lot of patients have been fearful of traveling through airports with medical marijuana because of the federal involvement," Sands said. "And you don't want to be hassled at the airports."

And although patients rely on their marijuana like they do any other medication, it may be intimidating for a traveler flying to a state where the drug is banned, Sands said.

"It'd be hard to expect the law enforcement there to be sympathetic," he said.

Kris Hermes, spokesman for the Oakland-based advocacy group Americans for Safe Access, argued a national policy would allow pot patients to avoid the patchwork of individual airport rules.

"It's clearly a good thing that airports such as Oakland and SFO allow patients to be able to travel with their medicine. That's a positive policy," Hermes said. "Some patients cannot be without their medicine for more than a few hours."

Bay Area News Group staff writer Josh Richman contributed to this report. Staff writer Mike Rosenberg covers San Mateo, Burlingame, Belmont and transportation issues. Reach him at 650-348-4324.