There is an ongoing “misunderstanding” between photographers and security of federal buildings. In general it *IS NOT* illegal to photograph any building including federal ones but photographers continue to get harassed for doing so. Carlos Miller has the US Department of Transportation’s official response which to the ACLU which makes this clear.
The bulletin makes it clear that there are no restrictions of taking pictures of federal buildings from the outside, especially if you are not standing on federal property.
I found this statement interesting though
The bulletin also states that it is permissible to photograph “building entrances, lobbies, foyers, corridors or auditoriums for news purposes.”
Apparently, if they have a problem with you, you get an extra out – news worthy-ness. Of course, as soon as they start to hassle you I think it becomes news worthy.