Medical marijuana users enjoy protection from criminal prosecution under California law — but that’s about it.

A medical cannabis patient can be fired solely for using the preferred drug at any time, and any medical marijuana user living in public housing can be evicted at any time.

And yes, this applies even in San Francisco. Although how likely it is that a joint will lead to homelessness depends on where exactly you live, or how much the local housing honcho hates you, activists and tenants say.

To understand exactly how this works, you have to understand that the San Francisco Housing Authority — the nation’s 17th largest provider of public housing, with 6,500 public housing units and another 9,557 Section 8 vouchers — hires private companies to manage as well as build some of its units.

Last week, tenants at Hunters View — a newly rebuilt development in Hunters Point — were outraged over a long list of “paternalistic” rules imposed by The John Stewart Company, as reported by the Examiner. The rules included regulations on bathing to combat a bedbug infestation, and also “strictly prohibited” the use or possession of marijuana, “even medical marijuana.”

Representatives from The John Stewart Company, which also manages Valencia Gardens on Valencia Street and North Beach Place on Bay Street, did not return telephone messages left Monday and Tuesday. But the company appears free to set any rules it pleases, even if those rules ban behavior that’s protected under state law.

A tenant-landlord agreement is a contract, and anyone is free to sign any contract they wish to sign. In tenant-friendly San Francisco, a sizable stack of laws and regulations dictate much of what a lease can and cannot say, but these laws do not appear to extend to medical marijuana. So if a Hunters View resident is a medical marijuana user, he or she is free to find other housing, or risk being evicted for taking their preferred medication.

“They sign a lease in the plain light of day,” said Housing Authority spokesman Rose Dennis. “They have to abide by that and they have to pay their rent.”

It’s long been suggested that Section 8 housing and the San Francisco Housing Authority are off limits to medical marijuana because the federal dollars that subsidize both are at risk. This doesn’t appear to be exactly true.

City housing policy bans the use of illegal drugs in public housing (though since many residents of transitional housing are struggling with substance abuse issues, it’s not always immediate grounds for eviction). Despite the fact that it’s a city agency, the San Francisco Housing Authority relies on federal law — the Controlled Substances Act — to determine what is considered an “illegal drug.”

And medical marijuana is most definitely an illegal drug under federal law.

City policy may change on that, Dennis tells us. She said that the Housing Authority is “monitoring the precedents” set by other public housing providers around the country. For what it’s worth, federal officials have ruled that neither public housing, nor landlords who take Section 8 vouchers are required to make “accommodations” for marijuana users.

Meanwhile, low-income folks who find themselves in public housing managed by John Stewart or directly by the Housing Authority must be crafty about their medical marijuana use, residents and activists say.

For example, relationships with neighbors or resident managers must be managed so that a batch of brownies or the smell of joint doesn’t lead to a complaint, said Greg Ledbetter, an activist with Black and Brown Just Cannabis Policy. He’s also affiliated with low-income marijuana users’ advocacy network Axis of Love.

“If I was in a wheelchair, they’d have to put a ramp for me to access my unit,” Ledbetter said. “So medical cannabis patients need their medicine. If I can’t smoke in my unit, then where is the place for me to smoke?”

The answer is the street. While it’s technically okay for medical cannabis dispensaries to let their customers smoke onsite, many dispensaries say they won’t allow onsite smoking so they can easily move through the permitting process. Several dispensaries that allowed onsite consumption have been shut down by federal Justice Department pressure during the year-long crackdown.

Any change in local policy, such as a provision allowing medical cannabis users to use marijuana in public housing without fear of eviction, would have to come from the Board of Supervisors. And the Board has barely touched medical marijuana — and is unlikely to do so anytime soon.