Basheshar Nath had agreed to a settlement of his tax liability under a provision of the Taxation on Income (Investigation Commission) Act, which let a taxpayer settle disputed income with the Investigation Commission instead of going through ordinary assessment. Years after accepting the settlement and paying under it, he challenged the very provision that allowed the settlement, arguing it let some taxpayers be treated more harshly than others assessed under the ordinary procedure, in breach of the equality guarantee in Article 14. The government argued that since he had voluntarily entered into the settlement and taken its benefit, he could not now be heard to challenge it, in effect saying he had waived his right to complain.
The Supreme Court, by majority, rejected this defence. The judges reasoned that fundamental rights exist not just to protect individual interests but also to serve a larger public policy, part of the basic scheme the framers built into the Constitution, so a citizen cannot simply give them up through consent, agreement or conduct, unlike a purely private contractual right that a person is generally free to waive. This reasoning is why the case is treated as the leading authority on the impermissibility of waiving fundamental rights in India.
This is a different question from the doctrine of eclipse, which is about reviving old inconsistent laws, the doctrine of severability, which is about cutting out only the invalid part of a statute, and the doctrine of territorial nexus, which is about a state's power to legislate on subjects connected to persons or things outside its borders.
The correct answer is the doctrine of waiver of fundamental rights.