I agree with Pohnpei's previous post. If a once-endangered species is proven to be thriving and sufficiently repopulating itself, I see no specific reason to continue a ban on hunting them. In Florida, the alligator was once considered an endangered species. After years of protection, alligators are now found in abundance; they have, in fact, become a nuisance throughout the state, and they are now hunted (and their meat sold) during specific seasons. Licensed alligator hunters can (I believe) hunt them during the entire year. Hopefully, another endangered Florida species, the manatee, will also repopulate itself through government protection. Unlike the whale and alligator, however, the manatee has little use for consumption or production.

Unless you are someone who opposes whaling on the basis of animal rights (that killing whales is similar, morally, to killing people), you would have to approve of countries resuming whaling if whale populations have truly recovered.

If the ban on whaling is meant solely to prevent them from becoming extinct, then surely whaling should be permitted if the whale populations are large enough to sustain the whaling.

The rest of your question seems to imply that you think these countries have cheated and should be punished for it.  That is a question that is separate from the one about the size of whale population.