Via:

Seven protesters were arrested after a pre-dawn raid on the Occupy D.C. camp in McPherson Square on Saturday, with dozens of police clearing away tents, debris and some dead rodents.

U.S. Park Police on horseback and on foot clad in riot gear swept into the park around 6 a.m. A helicopter circled overhead, horses’ hooves clattered on the pavement and protesters ran through the camp trying to wake up those still sleeping. Several square blocks downtown were closed for several hours because of the raid, which was characterized as “further enforcement” of a no-camping crackdown that began Monday.
...
Under the rules, protesters are allowed to conduct a “24-hour vigil” in the federal park, but are not allowed to camp overnight. But until recently, protesters had been openly camping at McPherson Square and a similar encampment in Freedom Plaza.

"If the US government enforced its banking laws like it did its park regulations, we wouldn't be
in this damn park in the first place."

– Occupy DC activist Todd Fine