By Jigyasa Pareek

Section 64 of the Patents Act, 1970, states that a patent may be revoked on a petition of any person interested or of the Central Government, or on a counter-claim in an infringement suit. Section 107, in turn, allows invalidity to be raised as a defence in an infringement action.

The statutory text, however, is silent on:

• whether a revocation petition under Section 64 can survive once invalidity is pleaded as a defence under Section 107 in a patent infringement suit; and
• whether a revocation petition can survive after the patent itself has expired.

Indian jurisprudence on this issue has been sparse. The earliest decision that tangentially touched upon the issue was the Calcutta High Court’s decision in Star Textile Engineering Works Ltd v. James Mackie Holding Ltd. [1977 SCC OnLine Cal 280]. There, relying on the UK Court decision in North Eastern Marine Engineering Co. Ltd. v. Leeds Forge Co. Ltd. [23 RPC 96], it was recorded that “though the patent has expired there is no bar for the Court revoking the same”. The observation, however, was merely noted as a submission of the counsel; the Court did not independently examine or conclusively determine the correctness of the proposition.

Decades later, the issue resurfaced before the Delhi High Court in Macleods Pharmaceuticals Ltd. vs The Controller of Patents & Anr. [C.O.(COMM.IPD-PAT) 38/2022], where the Court held that a revocation petition under Section 64 remains maintainable even after expiry of the patent and notwithstanding the plea of invalidity under Section 107 in a pending infringement suit. The judgment marked the first reasoned articulation in Indian law directly addressing the survivability of revocation post-expiry and its coexistence with a Section 107 defence. The decision was carried in appeal by Respondent No. 2, Boehringer Ingelheim Pharma GmbH & Co. KG, culminating in the Division Bench ruling in Boehringer Ingelheim Pharma GmbH & Co. KG vs The Controller of Patents & Anr. [LPA 129/2025; decision dated February 24, 2026]. The Division Bench not only affirmed the position taken by the Single Judge but also elaborated it by explaining the nature of a granted patent and revocation.

Boehringer’s central argument was that revocation presupposes a living patent. Once the patent expires by efflux of time, there is nothing left to revoke. To “revoke” an expired patent, it was argued, is akin to flogging a dead horse. It was further urged that Section 64 permits revocation only at the instance of a “person interested”. Once the corpus of the interest ceases to exist, the interest must also perish.

The Division Bench rejected these arguments at their foundation.

I. Whether revocation would operate retrospectively from the date of grant, or prospectively from the date of revocation?

The Division Bench unequivocally held that revocation under Section 64 operates retrospectively. A revoked patent is treated as though it had never been granted, void ab initio, dead from the very start. This conclusion was drawn from multiple strands of reasoning:

• Section 64 permits revocation either through a stand-alone petition or through a counterclaim in an infringement suit. Both avenues produce identical consequences.
• A counterclaim necessarily assails the validity of the patent from its inception because infringement actions typically involve claims for damages retrospectively. A counterclaim seeking revocation, therefore, cannot logically operate only prospectively, for that would leave intact the very foundation on which past liability is asserted. The survival of damages sustains the survival of revocation.
• The grounds for revocation under Section 64 are all defects that strike at the validity of the grant. A finding in favour of any such ground implies that the patent ought never to have been granted. Therefore, revocation under Section 64 dates back to the date of patent grant.
• Drawing from comparative jurisprudence, particularly UK Supreme Court’s decision in Virgin Atlantic Airways vs Zodiac Seats UK Ltd. [[2009] EWCA Civ 1062], the Division Bench emphasised that revocation is an act in rem that effaces the patent retrospectively. The Bench noted that patent law, by its very nature, operates in a transnational commercial ecosystem, and that Indian Courts ought to remain aligned with established global principles so long as they do not conflict with municipal law.

II. Whether a patent remains a patent till it is revoked, or till it is expired?

The Court observed that Section 2(m) of the Patents Act defines a “patent” as “a patent for any invention granted under this Act”. The statutory focus is on the act of grant, not on subsistence or enforceability. A patent, once granted, does not cease to be a “patent” merely because its term has expired. Expiry renders it unenforceable prospectively, but it does not extinguish its existence as a grant under the Act. A patent that has expired remains a patent for the purpose of Section 64(1).

The Court noted that Section 64 does not confine revocation to patents “in force”. Nor does it prescribe any limitation period tied to expiry. So long as the petitioner remains a “person interested”, the remedy remains available. In the present case, the existence of the pending infringement suit and the damages claim made Macleods’ interest self-evident.

III. Whether a revocation can be instituted, or can continue, after a Section 107 invalidity defence is taken in an infringement suit?

• A Section 107 defence allows a defendant to plead invalidity in an infringement suit. The finding operates inter partes and is transmitted to a supplemental record under Section 151(2).
• A Section 64 revocation (which may, prior to the institution of an infringement suit, be sought by way of a revocation petition, and after the institution of the infringement suit, by way either of a revocation petition or of a counter-claim) results in effacement of the patent from the Register, with transmission under Section 151(1). Its effect is in rem.

Importantly, the Court clarified that pleading invalidity under Section 107 does not extinguish the independent statutory right to pursue revocation under Section 64. However, consistent with Aloys Wobben, the Court clarified that a defendant cannot simultaneously pursue both a counter-claim for revocation and a stand-alone revocation petition for the same patent. The same is barred by the principle of res judicata. The Court affirmed all the reasons given by the Single Judge in differentiating between a revocation action under Section 64, and an invalidity defence under Section 107.