In April 2008, a group of less than 20 young people came to the memorial as part of a flash mob where they would dance to music played through their headphones.
U.S. Park Police then told the dancers to leave, and eventually arrested one woman on misdemeanor charges, Mary Oberwetter.
Oberwetter fought the charges in court, arguing that dancing was protected free speech, and noting that groups of noisy school children are routine at the memorial.
She lost that case, with the courts agreeing that the U.S. Park service has a duty to maintain decorum at the nation's monuments, and no demonstrations are allowed inside the monuments.
Earlier this month, the U.S. Court of Appeals for the District of Columbia upheld the earlier decision.
The group that gathered at the monument Saturday was there in protest of the upheld ban.
Saturday, May 28, 2011
Freedom of expression banned at Jefferson Memorial
Here's more background about the ban from another article concerning the arrest of Adam Kokesh and others for the crime of dancing in the wrong location: