From MyDD.

LOS ANGELES, November 9, 2004 - At 7:50 PM two armored tanks showed up at an anti-war protest in front of the federal building in Westwood. The tanks circled the block twice, the second time parking themselves in the street and directly in front of the area where most of the protesters were gathered. Enraged, some of the people attempted to block the tanks, but police quickly cleared the street. The people continued to protest the presence of the tanks, but about ten minutes the tanks drove off. It is unclear as to why the tanks were deployed to this location.

So who ordered that? If it was a local decision, shouldn't people be concerned that a local official has the authority to order tanks onto the streets of LA?

There is a video.