By Sanjay Raman Sinha
One of the world’s oldest mountain systems—the Aravallis—has once again become the site of a high-stakes legal and ecological contest. At the heart of the dispute lies an apparently simple, but deeply consequential question: What constitutes a mountain?
On November 20, 2025, a three-judge bench of the Supreme Court led by then Chief Justice of India BR Gavai accepted a proposal by the Ministry of Environment, Forest and Climate Change (MoEF&CC) defining an “Aravalli hill” as a landform rising at least 100 metres above local relief. This technical threshold, now known as the “100-metre rule,” would determine which parts of the Aravalli range qualify for statutory protection.
The implications are enormous. By introducing a height-based filter, the definition threatens to exclude vast stretches of low-lying ridges, knolls, and hillocks that together form the Aravalli ecosystem. Environmentalists and legal scholars view this move as a violation of both the Precautionary Principle and the Public Trust Doctrine—cornerstones of Indian environmental jurisprudence. The precautionary principle demands preventive action in the face of potential irreversible harm, even in the absence of scientific certainty.
Concerns have also been raised about the process through which the definition was adopted. The MoEF&CC panel’s recommendations were pushed through despite internal dissent, and affidavits filed before the Court reportedly lacked signatures of duly authorised officials—casting a shadow over the government’s intent.
In a dramatic turn, on December 29, 2025, a three-judge bench of the Supreme Court, headed by Chief Justice Surya Kant, stayed the Court’s November 20, 2025, order, acknowledging prima facie concerns with the narrow definition it had earlier accepted. The Court has now initiated a suo motu review, signalling a willingness to recalibrate the definition of the Aravallis based on ecological function rather than mere elevation.
This marks a return to earlier jurisprudence. In the landmark MC Mehta and TN Godavarman cases, the Supreme Court treated the Aravallis as a continuous geological and ecological ridge, not a collection of isolated peaks. The November 20, 2025, order had departed sharply from this settled understanding.
The stakes extend far beyond legal theory. The Aravalli hills are already under existential threat. A 2018 study revealed that 31 of Rajasthan’s 128 Aravalli hills have disappeared entirely, largely due to illegal mining. Experts estimate that the 100-metre rule would strip nearly 90 per cent of Aravalli landforms of protection.
Ecologically, the costs are staggering. The Aravallis recharge nearly two million litres of groundwater per hectare annually. Delisting low-height formations would accelerate groundwater depletion across Haryana, Rajasthan, and Delhi—regions already facing acute water stress. Yet, while ecological losses mount, mining interests, quarry operators, and real estate developers stand to gain.
With delisting, land rich in silica, marble, and granite would become legally accessible for extraction without the stringent forest clearances mandated for notified Aravalli hills. Low-lying areas—often the first to be mined or urbanised—would be opened up for commercial construction. State governments, particularly Haryana and Rajasthan, would benefit from increased revenues through mining leases and real estate development.
Stretching nearly 650 kilometres from Delhi to Gujarat, the Aravalli range has been under judicial scrutiny for over three decades. The legal battle began in the 1990s with a petition by MC Mehta, seeking protection of the fragile ecosystem. Since then, the case has evolved into a classic example of Continuous Mandamus, with the Supreme Court issuing ongoing directions, appointing expert committees, and monitoring executive compliance.
It is therefore ironic that a Court exercising long-term oversight would endorse a definition that it now appears compelled to revisit. Notably, the matter is currently being heard not by a larger bench, but by a three-judge bench comprising Chief Justice Surya Kant and Justices JK Maheshwari and AG Masih.
This review comes at a time when the Supreme Court has repeatedly stressed that once a point of law is settled by a bench, it should ordinarily be treated as final under Article 141 of the Constitution. Yet, recent departures from this norm are evident—most notably in the stray-dogs litigation and the Vanashakti case on post-facto environmental clearances.
In Vanashakti (2025), a two-judge bench held retrospective environmental clearances to be illegal, only for a larger bench to recall the ruling weeks later. Significantly, Justice Ujjal Bhuyan’s dissenting opinion warned against interpreting environmental law through “mechanical formulas” that reward violators.
The current bench appears to echo that warning. Chief Justice Surya Kant has already indicated that the Aravallis require a “nuanced and measured” assessment, rejecting a flat height-based formula.
State governments have argued that low-lying areas already mined or urbanised should be excluded from the Aravalli definition—an argument closely aligned with the logic underpinning post-facto clearances in Vanashakti. If the Court ultimately reworks the definition, it will unsettle both the November 2025 order and the Vanashakti precedent, necessitating a significant judicial course correction.
Such a correction would mean confronting entrenched governmental and commercial interests head-on. The environmental costs of protecting the Aravallis are undeniably high—but they cannot be weighed solely against short-term development priorities. To define a mountain narrowly is, in effect, to legislate its disappearance.
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