KyJim, that's definitely a concern if this technology goes forward. Hopefully the courts will see fit to not think the distinction is enough to uphold the use of the technology.
Well, other than the visible spectrum (which is visible, obviously), the boundaries between the various regions of the electromagnetic spectrum are largely man-made and arbitrary. This technology works on the same basic principle as night-vision equipment and thermal imagers, just at even longer wavelengths. If anything, the wavelengths being detected by these scanners are even further outside the range of normal human perception, so I think the same arguments will hold.
The "in public" versus "inside your own home" aspect does concern me, though.
EDIT - got my posters confused. I was responding to Al's point that the courts haven't specifically addressed terahertz imaging yet.