§ 511. Decisions of the Secretary; finality
(a)
The Secretary shall decide all questions of law and fact necessary to a decision by the Secretary under a law that affects the provision of benefits by the Secretary to veterans or the dependents or survivors of veterans. Subject to subsection (b), the decision of the Secretary as to any such question shall be final and conclusive and may not be reviewed by any other official or by any court, whether by an action in the nature of mandamus or otherwise.