And who should that be?
Professors in the field? High ranking individuals of certain groups (WAZA, AZA, EAZA, IUCN etc) - people that know their stuff and would be in my opinion qualified enough to choose these people.
Personally I think zoos that have very experienced reptile keepers should get the said reptiles, that way it is easily monitored and who gets them would be up to WAZA - who would simply decide by who they think would be the best zoo to have the species.
As for private breeders that is a different matter, since obviously it is much more difficult to monitor and choose who would be best suited. My only idea is that some sort of 'exam' in herpetology (and a difficult one at that) would have to be sat before they are issued with permissions to obtain 'new-to-captivity' species. But that isn't the best idea, and I'm sure that if anything came into practice somebody would know how best to chose - it's just that I don't