OK, here he is, 50 colonies. A perfectly legitimate beekeeper (all his hives are registered and bar coded or whatever), but very dishonest.
Oops, he lost 49 of them one winter, so big trouble ahead to replace and get a crop this year. Ahh, just pay the local night shift poachers/thieves/scum a small premium to collect 30+ hives from around the area, fill the legitimate bar-coded hives and burn, or otherwise dispose of, the stolen bar-coded hives.
OK, it might be a rediculous exaggeration (and apologies to anyone with 50 colonies out there, for using that number as an example), but for the odd hive nicked by the scum, the better way of proving things would be coded queens, coded frames and coded boxes (unless they were apprehended almost red-handed). When they know the boxes are coded, they will be finding ways around that little difficulty! Coded frames is out of the question for vendors, and coded queens is a legal minefield when we are talking about a relatively small number of thefts.
One single problem is knowing when they were nicked, especially when at out-apiaries, which may only be visited once or twice a week in the season, and perhaps once a month in the winter!
So, no, coding boxes would not particulay help nail the thieves, whether dishonest beekeepers, dishonest starters to beekeeping, or the quick-buck thieves who know where there is a ready market.
My view on compulsory registration of all hives is that it would be impossible to achieve and simply another jobsworth occupation. Most beeks are already on the radar, but every colony - no.
Regards, RAB