If a TSA agent stops you in an airport and starts asking questions, are you free to leave? What happens if you refuse to answer? Doesn't the 4th amendment require reasonable suspicion before a government agent can seize a citizen. I'll offer at least even odds that this SPOT program won't survive judicial scrutiny as is. This post links an interesting discussion of this question.

So, I wonder if a period of questioning by a SPOT guy (especially the MA State Cops in BOS) could be construed as a Terry Stop? Is someone's perceived behavior good enough to provide "reasonable suspicion that criminal activities is a foot [sic]."? I've read other stuff defining that there has to be a context for the "reasonable suspicion" and that a police officer has to be able to reasonable articulate why he or she concluded that a crime was about to be committed...

From this case, here is a pretty interesting argument against the SPOT program and the accusations of it being a "dragnet" for all sorts of thing unrelated to aviation security: