Revocation Operates In Rem And Dates Back To The Grant – The Patent Is Treated As If It Never Existed: Delhi High Court

“Revocation Effaces the Patent Ab Initio – Expiry Is No Sanctuary”, In a significant ruling clarifying the architecture of revocation jurisprudence under the Patents Act, 1970, the Delhi High Court on 24 February 2026 dismissed Boehringer Ingelheim Pharma GmbH & Co. KG’s Letters Patent Appeal and upheld the maintainability of a revocation petition even after expiry of the patent and despite the defendant having raised an invalidity defence under Section 107(1) in an infringement suit.

The Division Bench of Justice C. Hari Shankar and Justice Om Prakash Shukla in Boehringer Ingelheim Pharma GmbH and Co. KG v. The Controller of Patents & Anr., LPA 129/2025, decisively held that “revocation acts retrospectively and effaces the patent ab initio.” The Court further ruled that the expression “a patent” under Section 64 is not confined to a “patent in force,” and therefore expiry by efflux of time does not bar institution or continuation of revocation proceedings.

The appeal was dismissed, and the judgment of the learned Single Judge dated 15 January 2025 was affirmed.

Indian Patent No. 243301 relating to Linagliptin was granted to Boehringer Ingelheim with a priority date of 21 August 2002. On 17 February 2022, Macleods Pharmaceuticals Ltd filed a revocation petition under Section 64 of the Patents Act before the Delhi High Court.

Two days later, Boehringer instituted an infringement suit before the Himachal Pradesh High Court alleging infringement of the same patent. In its written statement, Macleods raised an invalidity defence under Section 107(1).

During the pendency of proceedings, the patent expired on 18 August 2023. Boehringer then sought dismissal of the revocation petition on two grounds: first, that expiry of the patent rendered the revocation petition infructuous; and second, that once Macleods had invoked Section 107 invalidity in the infringement suit, it could not continue the standalone revocation petition.

The learned Single Judge rejected both objections, prompting the present appeal.

The Bench framed two pure questions of law:

“Whether a revocation petition under Section 64 can be instituted or survive after the petitioner has raised invalidity as a defence under Section 107(1) in an infringement suit?”

“Whether a revocation petition can be instituted or continue after expiry of the patent sought to be revoked?”

Revocation Is Retrospective And Operates In Rem

The Court undertook an extensive analysis of Section 64 and its relationship with other provisions of the Patents Act.

Rejecting the appellant’s contention that revocation presupposes a subsisting patent, the Bench held that revocation necessarily invalidates the grant itself. It reasoned that since Section 64 permits revocation either by standalone petition or by counter-claim in an infringement suit, the consequence must be identical in both cases.

The Court observed:

“Revocation, if granted, takes effect from the grant of the patent being revoked. It is, therefore, rendered ineffective and incapable of assertion ab initio.”

The Bench emphasized that the grounds enumerated under Section 64 go to the root of the grant — lack of novelty, obviousness, ineligibility of applicant, misrepresentation, non-patentable subject matter — each of which implies that the patent ought never to have been granted.

In support, the Court relied upon the UK Supreme Court’s decision in Virgin Atlantic Airways Ltd v. Zodiac Seats UK Ltd, holding that revocation “deprived the patentee of the rights which the patent had bestowed on him as against the world; furthermore, it did so retrospectively.”

Thus, the Delhi High Court held that revocation under Section 64 “operates in rem and retrospectively from the date of grant.”

Expiry Of Patent Does Not Bar Revocation

A central plank of the appellant’s case was that once the patent had expired, it could not be “revoked,” as there was nothing left to revoke.

The Court rejected this submission, holding that Section 64 uses the expression “a patent” and not “a patent in force.” Referring to Section 2(m), which defines “patent” as “a patent for any invention granted under this Act,” the Court held that once granted, a patent remains a patent even after expiry by efflux of time.

The Court made a crucial distinction:

“The expiry of the life of the patent merely renders it unenforceable, and does not denude it of its character as a ‘patent granted under’ the Patents Act.”

Further, the Court reasoned that expiry during pendency of an infringement suit only extinguishes the right to injunction, not the claim for damages for acts committed during the subsistence of the patent. Since damages were claimed in the Himachal Pradesh suit, Macleods continued to have a “real and live interest” in seeking revocation ab initio to defeat the damages claim.

The Bench concluded:

“The revocation petition would continue to be maintainable even after the patent, of which revocation is sought, expires.”

Section 64 Revocation vs Section 107 Invalidity Defence: Distinct Remedies

The appellant relied heavily on Aloys Wobben v. Yogesh Mehra to argue that once invalidity is raised in an infringement suit, revocation cannot be pursued separately.

The Court rejected this interpretation.

It clarified that Aloys Wobben only prohibits simultaneous pursuit of a revocation petition and a counter-claim seeking identical relief. It does not equate a Section 107 defence with a counter-claim for revocation.

The Bench drew a sharp distinction:

“A revocation petition, if it succeeds, removes the patent entirely from the register of patents… The decision operates in rem.”

In contrast:

“The highest that would result, if the Section 107 defence succeeds, is that the suit would be dismissed. The patent does not stand removed from the register.”

The Court relied upon Section 151 of the Patents Act, which differentiates between transmission of revocation orders and transmission of findings in infringement suits. A successful Section 64 petition mandates entry in the Register of Patents; a successful Section 107 defence results only in entry in a supplemental record.

Thus, the remedies are distinct in nature, scope and consequence, even if the grounds may overlap.

On “Person Interested” After Expiry

Addressing the argument that expiry extinguishes the status of “person interested,” the Court held that Macleods, being sued for infringement and facing damages claims, had a continuing and substantive legal interest.

“Revocation, if it succeeds, would invalidate Boehringer’s patent in the suit from inception… Macleods has a real and live interest in seeing that its revocation petition succeeds.”

Therefore, Macleods remained a “person interested” within Section 2(1)(t).

The Division Bench affirmed the Single Judge’s order and held:

“A revocation petition would be maintainable, and would continue to survive, even after the patent of which revocation is sought expires by efflux of time.”

“A revocation petition can be instituted even after a Section 107 invalidity defence is taken in the infringement suit.”

The appeal was dismissed with no order as to costs.

This ruling settles two recurring procedural controversies in Indian patent litigation:

First, that expiry of a patent does not render revocation academic, particularly where damages claims survive.

Second, that Section 64 revocation and Section 107 invalidity defence are doctrinally distinct remedies, and raising one does not extinguish the other.

By recognizing that revocation “effaces the patent ab initio,” the Court has reaffirmed the in rem character of Section 64 proceedings and preserved the structural integrity of patent revocation jurisprudence under Indian law.

Date of Decision: 24 February 2026