An attorney for Cindy Sheehan told a federal appeals court panel Tuesday that the Iraq war protester's 2005 arrest outside the White House gate during an anti-war demonstration was unconstitutional.

Sheehan, whose son was killed in Iraq while serving in the Army, was among several hundred protesters arrested Sept. 26, 2005 on the sidewalk in front of the White House despite calls from police to disperse. Sheehan was seeking a meeting with President Bush.

The protesters were charged with demonstrating without a permit. A magistrate judge later found the group guilty and each was given a $50 fine and a $25 fee. Sheehan's conviction was upheld by another judge, and she appealed to the U.S. District Court of Appeals for the D.C. Circuit.

At issue is what Sheehan knew about the demonstration before it took place and whether her actions that day should have subjected her to arrest by the U.S. Park Police.

A group called Iraq Pledge of Resistance organized the event and obtained a permit from the National Park Service, according to her court filings. Sheehan's Gold Star Families for Peace group was not part of planning the event or the permitting process.

That permit was later changed so that it no longer included the sidewalk outside the White House where Sheehan was eventually arrested. Her attorneys say it was retracted by the National Park Service, but government lawyers say it was voluntarily withdrawn.

Sheehan therefore was allegedly not aware of the permit's limits and stipulations when she sat on the sidewalk before her arrest. National Park rules on permits violated her First Amendment right to free assembly and speech because they allow for arrest regardless of whether a protester is aware of permits, Sheehan claimed.

"It is extremely unlikely that one person or a group of people who show up at a demonstration are going to have any idea whether there is a permit," Catherine Carroll, Sheehan's lawyer, told the three-judge appeals court panel.

But a government attorney pointed out that police warned Sheehan and other protesters several times through a bullhorn that they were demonstrating without a valid permit and were subject to arrest. That alone should be enough to prove she knew she was violating the law, said Florence Pan, an assistant U.S. attorney.

"They wanted to be arrested in order to support their cause," Pan said of the demonstrators.

The appellate judges appeared to focus on the significance of the bullhorn warnings from police. But Judge Harry Edward's challenged Pan on how much the government could prove about Sheehan's intent and what she knew about the protest permit.

"You haven't shown she did not know the valid permit was no longer valid," he said.

Sheehan was not present at Tuesday's hearing. At the 2005 incident, she carried a photo of her son, Casey, who was killed in 2004 in Baghdad. The first one arrested, she smiled as she was carried away to chants of "The whole world is watching" from other protesters. She was arrested again a year later at the White House while trying to deliver a petition.