There are plenty of sources online for buying legal polar bear hair. A quick google search and I found several sites in the US advertising legal polar bear fur. Plus a few in Canada. For officers to spend government funds to set up such a sting there must have been something else we are not being made aware of. I just cannot picture officers going from fly shop to fly shop peddling a polar bear skin until they got someone to fall for their evil scheme.
Besides sticking your fly into your shirt to check whether it is barbless like some of them do now. Do we now have to worry about Conservation officers going around checking the DNA of each fly on your hat for Pre 1972 fur?
They couldn't search your fly box without probable cause. I suppose polar bear sniffing dogs could be trained for work in the field.