Mike, I guess I must be missing something here. Is the Patriot Act in effect here? Is this a matter of national security? Is the park public property? Is the "Bean" public property? Are there laws which say you cannot use a tripod, as in Mexico or some places in europe?
My understanding of public property is that photography is allowed in a public park at any time in which the park is open, day or night. A tripod does not make a professional (see my gallery, I use a tripod but am certainly not a professional). What is the real issue here about the use of a camera on public property. Is it the "bean"? If an artist has a work on display on public property, there are no laws about taking the picture. There are laws about the use of an image in which a copyright has been used wrongfully, but that is certainly not a police issue, it is a matter for the courts to decide.
I still suggest a large "shoot-in" by as many LF photographers as possible. tim