Can the doctrine of *rebus sic stantibus* be applied to inter-State river water allocations within a federal polity? Examine with reference to the Cauvery dispute.

The doctrine of rebus sic stantibus is written into Article 62 of the Vienna Convention on the Law of Treaties [4]. It allows treaty obligations to be revisited after a fundamental and unforeseen change of circumstances. Karnataka has now reserved the right to seek reopening of the Cauvery allocation, citing India's own stand on the Indus Waters Treaty [1]. In a federation, the doctrine applies only in part, and only through adjudication.

Why the doctrine does not transplant directly

• Consent vs adjudication: a treaty rests on the consent of the parties. Cauvery shares were never agreed. The CWDT decided them (referred 1990, award 2007), and the Supreme Court modified them on 16 February 2018 [2]. They are a judgment to obey, not a contract to renegotiate.
• Finality: a notified tribunal decision carries the force of a Supreme Court decree [6]. If one State could reopen it alone, the scheme of Article 262 and the 1956 Act would be weakened.
• High threshold: even between nations, the ICJ rejected Hungary's changed-circumstances plea in Gabčíkovo–Nagymaros [5]. Growing demand alone is not a "fundamental" change.
• Weak analogy: the Indus Treaty's abeyance is linked to cross-border terrorism [1]. Nothing similar exists between federating units.

Where "changed circumstances" has legitimate space

• Shares are not frozen: the Supreme Court gave Karnataka an extra 4.75 TMC for Bengaluru's drinking water and 10 TMC of Tamil Nadu groundwater that had not been counted [2]. Allocations can be recalibrated through adjudication.
• Real shifts: urban growth, climate variability and groundwater stress have changed the facts since the data base of 1990.
• Karnataka's own framing: its reply speaks of revisiting shares "by agreement or adjudication" [1]. That supports a structured review, not unilateral reopening.
• Credibility caveat: the plea came in reply to Tamil Nadu's complaint about a release backlog [1]. It can look like a shield for non-compliance.

Way forward

• Enact the ISRWD (Amendment) Bill, 2019. It provides a Disputes Resolution Committee and a 2+1-year deadline for tribunals [7], so awards are less out of date by the time they arrive.
• Add a periodic-review clause to the Cauvery Water Management Scheme, with the CWMA keeping shared rainfall, flow and groundwater data.
• Keep releases going while any review takes place.

Rebus sic stantibus cannot be imported wholesale into federal water law. Its core idea can be: allocations must respond to changed hydrology. A time-bound, scheduled review would balance finality with equity. That fits cooperative federalism and SDG 6 (clean water and sanitation).