I'm wondering about this question myself. It's not as if the facts of your identity change because a country revokes a document. Is it just a policy issue, that there are no countries that allow entry without showing a passport?

It certifies his identity, not his rights. I'm not sure how you can suddenly claim it's not valid, without claiming that the original certification was found to be incorrect.

It sounds like the old Russian system where you couldn't leave the country without a passport (and it was made very hard to get one).

It means that it is made not valid by the issuing country.