To hear anti-war demonstrators tell it, it's getting harder to be arrested in this town, even when you want to be.

Last Saturday during the mass demonstration at the Ellipse against the Persian Gulf War, a group of 50 to 75 protesters marched to the south side of the White House, lay in E Street NW in a symbolic "die-in" and waited to be arrested for blocking traffic -- a classic exercise in civil disobedience.

Nothing happened. U.S. Park Police, who had routed traffic away hours earlier, surrounded the group but did not make arrests. After two hours of waiting with temperatures dropping into the mid-thirties after sunset, the group got up and went home.

Whether intended or not, the police refusal to make arrests had the effect of undermining the purpose of the civil disobedience: to deliberately violate the law and seek arrest to dramatize what the participants felt was a greater evil, the war in the Middle East.

"The police frustrated the CD {civil disobedience} action," said one participant, Gary Johnson, 33, a Washington Peace Center volunteer. "There were no arrests {in that area} and no media reports of arrests."

Leaders of the National Campaign for Peace in the Middle East, which sponsored Saturday's anti-war rally, say they suspect police intentionally avoided arrests there to undercut the civil disobedience effort.

Park Police acknowledge they made a tactical decision not to arrest, but said it was done to avoid tying up dozens of officers in protracted arrest and booking procedures.

"We were concerned that if we committed a lot of officers to arrest and processing, other {demonstrators} might try to hit the gates around the White House," said one police official, who asked not to be identified.

"If there was a political decision," he said, "it was to keep the White House open."

The civil disobedience effort started as the main rally on the Ellipse was breaking up. About 50 to 75 protesters, divided into small "affinity groups" of mutual friends, marched north onto E Street, heading toward the southwest gate of the White House.

Lisa Fithian, a campaign coordinator and leader of the civil disobedience group, carried a hand-held siren, which she was to use as a signal for the group to begin its "die-in."

About 100 yards from the gate, Fithian said, the group encountered a line of horse-mounted police and could go no farther.

Johnson said he heard the siren go off, and he and other participants began screaming and falling onto the street, "expressing symbolic death" from air raids in the Middle East.

Police surrounded and isolated the participants, pushing several hundred of their supporters back to the edge of the Ellipse and keeping reporters and photographers out of the area.

A bus and two police vans were pulled up, blocking any view of the "die-in" from the Ellipse.

"Our idea was to stay till we were arrested," said Johnson.

But after about two hours, he said, "The ground was getting very cold . . . . We knew we weren't going to get arrested," so the group left.

Since protests began with the outbreak of war Jan. 16, both D.C. and Park Police have exercised flexibility in avoiding arrests.

On the night of Jan. 16 and again on Jan. 17, when hundreds of chanting demonstrators poured into the streets surrounding Lafayette Square near the White House in impromptu marches, police made no effort to stop them.

Instead, police shepherded them along, closing off traffic at intersections ahead of the demonstrators and keeping the streets cleared until the protesters returned to Lafayette Square.