SAN FRANCISCO (AP) — Civil libertarian groups have backed away from threats to legally challenge the Bay Area Rapid Transit system’s wireless service shutdown last week after the agency refused a repeat amid rush-hour protests that shuttered four San Francisco stations.

The American Civil Liberties Union met with BART’s police chief late Monday even as demonstrators protested the agency’s action to block wireless reception Thursday to disrupt a planned protest against police brutality. After the meeting, ACLU attorney Michael Risher said the organization had no plans to file a lawsuit, but he remained disappointed that he didn’t extract a pledge from BART to refrain from similar tactics in the future. He said he planned to continue meeting with the agency.

The Electronic Frontier Foundation, too, said it was unlikely to file a lawsuit over the disabling of wireless reception for three hours.

Still, the shutdown of wireless towers in stations near the protest Thursday raised questions about the role that social networks play in helping people, from Egypt to London, organize online. In the U.S., with its history of free speech, critics are saying BART’s move was unconstitutional.

Cellphone service was operating Monday night as an estimated 50 protesters gathered on the Civic Center Station platform chanting “no justice, no peace” shortly after 5 p.m. Thirty minutes later, police in riot gear and wielding batons closed the station and cleared the platform after protesters briefly delayed an east-bound train from departing.

From Civic Center, the protesters were joined by more demonstrators and marched down San Francisco’s Market Street and attempted to enter to more stations. Officials closed those stations as well.

“Once the platform becomes unsafe, we can’t jeopardize the safety of patrons and employees,” BART Deputy Police Chief Dan Hartwig said.

Hundreds of people stood on the sidewalks and streets outside stations in the city’s Financial District on Monday evening. Many of the people appeared to be commuters.

Elijah Sparrow, a protester, called the demonstration “one of the defining battles of the 21st century over who is going to control communication.”

BART officials have said their primary concern was to ensure that passengers are safe.

“It’s wrong,” the ACLU’s Risher said. “There were better alternatives to ensure the public’s safety.”

Former BART director Michael Bernick applauded the move, saying it ensured a safe and uninterrupted commute Thursday night.

“Finally, BART said enough,” said Bernick. “BART put its riders and commuters ahead of these protesters and the ACLU.”

BART cut power to its wireless nodes Thursday night after learning demonstrators planned to use social media and text messaging to protest police brutality. The tactic appeared to work because no protest occurred.

BART’s actions prompted a Federal Communications Commission investigation, and a hacking group organized an attack on one of the agency’s websites on Sunday, posting personal information of more than 2,000 passengers online. The group Anonymous called for a disruption of BART’s evening commute Monday.

“We are Anonymous, we are your citizens, we are the people, we do not tolerate oppression from any government agency,” the hackers wrote on their own website. “BART has proved multiple times that they have no problem exploiting and abusing the people.”

BART spokesman Jim Allison said BART has notified the FBI, and that no bank account or credit card information was listed.

BART officials, meanwhile, defended the shutdown of the cell service as a legal approach to ensure commute safety.

A protest last month on a San Francisco platform calling for the dismissal of the transit officers responsible for the July 3 shooting death of a man wielding a knife prompted the closing of one station and caused system-wide delays during rush hour.

Allison said the wireless outage was only for platforms and trains running under the city, places where protests are banned.

By Monday, a growing number of free speech advocates were calling on BART to renounce the tactic, with many calling the action an unconstitutional attempt to stifle lawful protest.

Regardless of its strict legality, Tien said the tactic was unsavory and compared it to former Egyptian President Hosni Mubarak’s shutting down access to the Internet in a failed attempt to stop civil unrest.

Bernick, the former BART director, said Northern California governments such as BART have been struggling for years with how to handle vocal political demonstrations that often escalate to violence.

BART and Oakland, in particular, have experienced several large-scale protests that turned into riots after a white transit officer shot the unarmed black commuter Oscar Grant on New Year’s Day 2009.

BART officials said they are working on a plan to block any efforts by protesters to disrupt the service, which carries 190,000 passengers during the morning and evening commutes every day.

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Associated Press writers Terry Chea in Oakland and Terry Collins in San Francisco also contributed to this report.

Copyright 2011 The Associated Press.