Certain areas in public space during special events etc are deemed as being "free speech zones" in expectation of people exerting "free speech." Protestors or whoever are supposed to stay in these zones, although the zones may not be clearly marked or pointed out to people planning on using "free speech." If a police officer or valid security person tells you to shut up and move away, and you do not, you can be arrested for using "free speech" outside of the "free speech zone."

Had this happened in the White House press room, she would not have been arrested. Had this happened in the 12x12 "free speech zone" in a public park where the dignitaries were speaking, this would not have happened (the zone would have been over a hill and behind some trees, btw).

These laws usually expire after the event, unless we are talking about somewhere that is a parmanent fixture. For Example, the cameras can harass the congress on the Capital steps, but not inside the doors.

I'm not saying I like any of this, its just how it is. Some old lady was arrested at a Bush event a few years ago for leaving the "free speech zone" in a park or something. Hillary Clinton also used it quite liberally, in to changing the setup of the event so cameras would be pointed away from free speech zones if they were to focus on the event, she did it by narrowing the spots for cameras to be placed, a real zoning expert she. Don't know about presidents before them, wasn't paying attention