The Repairmen of Cyclops

The Corps Galactica, the Galaxy's police force, had pledged itself to a policy of non-interference with the backward Zarathustra Refugee Planets. Langenschmidt, the Corps chief on the planet Cyclops, was content with this ruling. After all, if the refugee planets could form their own civilizations from scratch, logically they would come up with cultures suited to their own needs. However, when the case of Justin Kolb came to his attention, Langenschmidt was forced to rethink the problem.
Kolb's accident with the wolfshark revealed to the Corps' medicos the leg-graft that had been performed on him. It was a perfect match - only its gene-pattern wasn't Cyclopean, and limb-grafting wasn't practised on Cyclops. Where had the leg come from, who had been the unknown repairmen, and wasn't this something that might be violating galactic law?(First published 1965)