Warned that they were risking possible police citations and arrest, Pete Irving responded defiantly.

"This is as much of a job as I have," he said. "I’ll take my chances."

Just about then a police cruiser appeared and an officer pointed at the couple and told them in no uncertain terms to move on.

Move on they did, at least for the time being.

A year after a controversial ordinance prohibiting sitting or lying on San Francisco sidewalks was first proposed, police are now enforcing the new law along the city’s most famous thoroughfares.

Yet, vigorous squabbling continues between supporters who claim the "sit-lie" law is working and opponents who argue it unfairly targets the homeless, day laborers and mentally ill.

Opponents went so far as to build wooden benches and placing them on corners — so that sidewalk squatters could sit — created a Facebook page to register their protests.

According to the most recent official statistics available, between March 26 and April 1, police across the city handed out eight citations and issued 75 warnings. They also responded to 16 calls complaining about violators who were gone when officers arrived.

Last fall, San Francisco voters approved Measure L which prohibits sitting or lying on sidewalks between 7 a.m. and 11 p.m. But police delayed enforcing the law until last month to ensure officers were properly trained.

The protocol says that officers will issue a written warning before citing anyone. Fines for repeat offenders range from $50 to $500 and possibly jail time.

"The emphasis is not to cite, but to inform and offer services," said Sgt. Mike Andraychak, a police spokesman.

The initiative was proposed by former police chief and now District Attorney George Gascon after mounting concerns about those who clog sidewalks or otherwise threaten or intimidate pedestrians. He eventually got former Mayor Gavin Newsom on board.

Merchants, especially in the once hippie-crazed Haight-Ashbury neighborhood, led the charge, complaining about overbearing young transients blocking patrons with aggressively panhandling, sometimes with big dogs at their sides.

Judah Collins, co-manager of a music store, said he typically told stragglers about five times a day to stop hanging out by his storefront. Now, it’s down to a couple of times or so, he said.

"I see both sides of the coin," said Collins about the law. "It must be working and intimidating a lot of people."

Alan Bendit, a fellow co-manager, has a different take.

"The cops are selectively choosing who to ticket," Bendit said. "I’m not so convinced."

Capt. Denis O’Leary, whose station patrols the area, said there has been vigorous enforcement since late last month. This month alone, his officers have issued at least one "sit-lie" citation a day.

"Quite frankly, I didn’t know what to expect," O’Leary said. "I’m finding that when I walk that beat, the folks getting cited are those who have other issues. They either drink too much, use too much drugs or have a mental illness.

"I’d rather have my officers focused on more serious crimes."

But, he said, "It is a valid law that has to be enforced. We can’t ignore it no more than if someone ran a stop sign or a red light."

Ted Loewenberg, president of the Haight Ashbury Improvement Association, said he’s noticed significant changes in his neighborhood since the law has been enforced. He recently saw officers call an ambulance for an intoxicated man instead of issuing him a citation for sitting on a curb.

Loewenberg believes there will be an adjustment period, noting he still sees large groups of young transients congregating on certain corners like Haight Street and Masonic Avenue.

"Police have to be vigilant and when that doesn’t occur, it’s going to take folks like me to kindly remind them," Loewenberg said. "That’s why there’s a citywide law."

Bruce Wolfe, vice president of the Haight Ashbury Neighborhood Council, said the sit-lie law simply won’t work. He still believes the ordinance is unconstitutional.

"It seems a little bit overextended, overreaching. I just find to make everybody have to be on their two feet moving and walking seems very odd for a city to demand," Wolfe said. "That it would have this huge drastic effect on changing the social landscape of the city, I just don’t see it.

"The voters had the wool pulled over their eyes on this one."

Recent arrivals Joe Lust, 20, of Austin, Texas, Liz Mallion, 22, from Hawaii, and Steven Grossman, 21, of Fort Collins, Colo., said they have quickly learned the nuances of the "sit-lie" law.

That includes watching for police and standing up on a second’s notice.

On Wednesday, they debated whether to plop down on a corner to play music, or join the passing throngs heading to celebrate "4-20," the unofficial marijuana holiday, at Hippie Hill in nearby Golden Gate Park.

"This is public space," Lust said. "There’s a new law, but I still don’t understand it. Why can’t we sit here?"

As police cars and vans passed by, two vehicles slowed down, with officers taking a look. The trio decided to amble on toward the park.