I went to the federal building on Wilshire to get some night shots when security stopped me. I asked them whether what I was doing was illegal and they pointed me to some GSA rules, which I read. Here are the rules in part:
Photographs for News, Advertising, or Commercial Purposes (41 CFR 102-74.420) Except where security regulations apply, or a Federal court order or rule prohibits it, persons entering in or on Federal property may take photographs of:
(c) Building entrances, lobbies, foyers, corridors, or auditoriums for news purposes.
So I am allowed to take pictures of the inside and outside of the building. Pointing this out, I was told “not to look for trouble” and asked to leave. Reiterating once more that their rules stated I was actually allowed to take pictures didn’t seem to get through to them, which is to be expected. So I went across the street.
Al-Qaeda, have at it.

For future reference, here’s a link to The Photographer’s Right.
The Security Guards hate our freedom.