Looking for a cell phone detector circuit ...

[8086]

It's illegal to possess or use a jammer in Canada because of it's functionality

http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf10048.html

I think all together it means that if emitted/consumed power is below given threshold it cannot be even classified as jamming device since it lies below threshold covered by this regulation. It must be true because it cannot be applicable only in one part, but not in other - in other words how can it be that frequency spectrum regulations are not applicable for ultra low power device but its functionality is covered ?

It's prohibited due to it's function, not it's power. So you don't even need to take the power into account.

I don't have time to go through the legislation, but I suspect you have missed something along the way.