Citizens of the Most Liberal City in America are suffering a crisis of conscience. San Francisco Mayor Gavin Newsom is asking them to approve a law that would make it illegal to sit or lie down on a sidewalk.

For San Franciscans, who are famously permissive of almost everyone, including the homeless (who would be impacted most), the proposal goes to the heart of their identity. It’s as if Daytona Beach outlawed American flags and 20-ounce to-go cups.

For Seattleites, though, this is old news. Because Newsom is modeling his law after the one passed in 1993 by then–City Attorney/street-sweeper Mark Sidran.

Newsom’s legislation is more far-reaching. Where in Seattle it’s only illegal to take a nap downtown during business hours, San Francisco’s law would make sidewalk siestas illegal across the entire city, 16 hours a day.

But if our Bay Area friends are worried about appearing hostile to the less-fortunate, they might take what’s happened in Seattle—or more specifically, what’s not happened—to heart.

Comprehensive enforcement stats for our city’s sit/lie ordinance aren’t available. But City Attorney spokesperson Kimberly Mills was able to provide Seattle Weekly with a snapshot of 2009, in which only 57 infractions were handed out and 23 ended up in charges, half of which were eventually dismissed.

Compare that to a law that gets violated a lot—like the nearly 5,000 people charged last year for driving with a suspended license—and Mills says you can tell Sidran’s law is not enforced all that often.

Not that this will make it any easier to persuade San Francisco to lie down for Newsom’s new law. But it should make its citizens feel more secure to know that America’s Second Most Liberal City didn’t lose its cred after passing something similar.