Sitting on the walls is now banned in Rittenhouse Square.

The perching prohibition went into effect Thursday, confusing - but not stopping - about a dozen people who gathered to enjoy the park on the unseasonably warm January day. Four signs had been installed in the interior of the park along with several new no-smoking signs, aimed at what neighbors have called a chronic problem of marijuana use.

The Department of Parks and Recreation authorized the new rule and the signs' installation in conjunction with police and the Friends of Rittenhouse Square group.

The city directed questions about fines or penalties to police, who did not immediately return requests for comment.

"The move was in response to a recent uptick in vandalism on the historic balustrades, which received nearly $1 million in restoration work just a few years ago," the Department of Parks and Recreation said in a statement. "Furthermore, the walls were not originally designed to be used for seating, so this measure will further protect the structural integrity of these iconic park features."

The Friends of Rittenhouse Square have argued that the 3-foot-high walls, which often draw large groups of people, promote drug use.

In October, wall loitering came up several times at a community meeting attended by more than 300 people. One attendee asked whether anything could be put on the ledges to stop people from sitting there. She suggested planters.

Police officers acknowledged at the meeting that enforcement of no-smoking rules in the park had lagged, and they pledged to crack down on marijuana use. The meeting grew out of a shooting in the park Oct 18., in which a bike messenger was shot five times trying to intervene in a robbery. Police have said the shooter knew the people he was trying to rob and called the robbery an isolated incident.

On Thursday, as dusk set in, a trumpet player let the notes of "What a Wonderful World" fall over the park and a woman gave out free coffee from a table she had set up near relaxing bike messengers.

About a dozen people sat on the walls, some not realizing the signs had gone up. Neither a security guard nor a police officer in the center of the square asked them to get down.

"What signs?" asked Dori Markovitz, 18, when approached by a reporter. "Oh, I didn't even see that. That's stupid. That makes no sense."

She stayed put, catching up with a friend.

Nearby Corey Griffith, 33, of South Philadelphia, sat on the wall, legs dangling near the sign forbidding such activity.

"Literally, I think there will come a time in the summer where there is a protest in which you will not see a part of this wall without a person sitting on it," Griffith said.

"Sitting in Rittenhouse Square is Rittenhouse Square," he said. "I saw that sign, and I was like [expletive] that sign. It's preposterous."

Griffith used to live near Washington Square Park, which has no such walls, and he marveled at how much more lively Rittenhouse becomes with the seating.

"Rittenhouse is a neighborhood, but the square is so big that I feel like it transcends the neighborhood. I think it's the seating that makes it. If no one can sit on walls, kids aren't going to bring lawn chairs," he said.

Asked about whether he thinks it will cut down on drug use in the park, Griffith smiled.

"We literally just smoked pot - you can quote me on that."

215-854-5506 @jterruso