“Can one kill a dead body?” The metaphor — flogging a dead horse, revoking an expired patent — is irresistible, and it framed Boehringer Ingelheim Pharma GmbH & Co. KG v. The Controller of Patents & Anr. [LPA 129/2025, decided 24 February 2026], where a Division Bench of the Delhi High Court held that yes, you can revoke a patent that has already expired — and that the revocation reaches all the way back to the day it was granted. The Bench affirmed and elaborated the Single Judge’s ruling in Macleods Pharmaceuticals v. Controller [C.O.(COMM.IPD-PAT) 38/2022].
The argument: nothing left to revoke
Boehringer’s case was structurally elegant: Section 64 revocation presupposes a living patent; once a patent expires by efflux of time there is nothing to revoke, and once the patent is gone the “person interested” has no surviving interest. The Division Bench rejected the premise. Indian authority on the point had been thin — the Calcutta High Court’s 1977 decision in Star Textile Engineering v. James Mackie had merely noted (as counsel’s submission) that expiry is no bar to revocation — so the Bench built the answer from first principles.
Revocation is retrospective, and an expired patent is still a “patent”
First, the Court held that revocation under Section 64 operates retrospectively: a revoked patent is treated as if never granted, void ab initio. The reasoning is tight. Section 64 allows revocation by petition or by counterclaim, and the two must have identical consequences; an infringement counterclaim necessarily attacks validity from inception, because damages are claimed for the past — so revocation cannot be merely prospective without leaving past liability hanging on a patent later found bad. Every Section 64 ground is a defect going to the validity of the grant, implying the patent ought never to have issued. The Bench drew on the UK Supreme Court line in Virgin Atlantic Airways v. Zodiac Seats UK [2009] EWCA Civ 1062 that revocation is an act in rem effacing the patent retrospectively, observing that Indian courts should stay aligned with global patent principles where municipal law permits.
Second, on whether a patent stays a “patent” after expiry, the Court turned to Section 2(m), which defines a patent as one “granted under this Act” — the focus is the act of grant, not subsistence. Expiry makes a patent unenforceable prospectively but does not erase its existence as a grant; it remains a “patent” for Section 64(1), which is not confined to patents “in force” and carries no limitation period tied to expiry. So long as the petitioner is a “person interested” — here, self-evident given the pending infringement suit and damages claim — the remedy survives.
Section 64 and Section 107 are not the same animal
Third, the Court mapped the relationship with Section 107. A Section 107 invalidity defence operates inter partes and is transmitted to a supplemental record under Section 151(2); a Section 64 revocation effaces the patent from the Register in rem, with transmission under Section 151(1). Pleading invalidity under Section 107 does not extinguish the independent statutory right to seek revocation under Section 64. But, consistent with Aloys Wobben v. Yogesh Mehra , a defendant cannot run both a counterclaim for revocation and a stand-alone revocation petition for the same patent — res judicata bars the double shot.
Why it matters
This is now the leading Indian statement on a recurring puzzle, and it has real bite. Generic challengers can clear lingering, expired-but-once-asserted patents off the Register with in rem effect, useful where damages for the patent’s lifetime are still in play; patentees can no longer treat expiry as a safe harbour from validity scrutiny. Read with this blog’s note on the Division Bench’s Novo Nordisk exposition of Section 64(1), the contours of Indian revocation law are finally coming into focus — retrospective in effect, in rem in reach, and available even when the patent itself has breathed its last.
Sources & further reading: Section 64; Section 107; Section 2(m); Virgin Atlantic v. Zodiac; Aloys Wobben v. Yogesh Mehra.
Educational note: This case summary is general information, not legal advice.