The movement is coming home.
San Francisco is widely seen as the cradle of America's medical cannabis industry, which has grown far and wide since the days when Dennis Peron opened the first cannabis club (illegally) in the late 1980s in the Castro district to help gay men dying of AIDS.
On Saturday, homage will be paid to this heritage -- medical pot has become legal in 19 other states since California's landmark 1996 law -- when former Mexican President Vicente Fox headlines the International Cannabis and Hemp Expo at Civic Center Plaza.
Up to 5,000 people are expected at the event, the fifth such expo but the first in San Francisco, after a pair of events at the Cow Palace, one in Oakland and another in Burlingame.
There will be marijuana consumption but no smoking -- vaporizing only, and only for medical marijuana patients who have their doctor recommendation handy.
Some of San Francisco's licensed dispensaries also will be distributing cannabis and cannabis products -- in full view of City Hall and in full compliance with local law.
"This is about people who are sick and are choosing an alternative medicine," said event organizer Melinda Neal, who was a staunch opponent of the drug until her husband became ill with cancer. "It's about recognizing this incredibly powerful plant ... and not being afraid of it."