I think it's implied they were not arrested. What law did they
violate?

"Hauled off in handcuffs" normally implies an arrest.

And in post-terrorist America, there will easily be *some* law that can be
stretched to fit.

If media goes undercover to a used car dealer to show how buyers can
get screwed, you'd probably agree with that. If they go undercover to
an FBO under circumstances which were obviously suspicious, what's the
difference?

Because they were in effect a false alarm in a time of public danger.