Whatever happened to the days when security clearances were revoked automatically if you were not actively working in a position that required one?
If the Admiral is retired then he does not need a security clearance.
The tradition is that senior fellows, who might be called on again for their expertise, might be kept ‘in the loop’. It is part of maintaining a knowledge pool instead of throwing it out with a retirement or an election.
No one from this administration is asking Brennan anything.
Moreso, it is not in any way an entitlement.