Unjustified Patent Enforcement

MIPLC Master Thesis Series (2017/18)

80 Pages Posted: 11 Sep 2019

Date Written: September 12, 2018


This thesis analyses the legal consequences of subsequent patent invalidation on infringement actions, contracts and warning letters.

Patent invalidation has a retroactive effect. The revoked patent should be treated as has never exist while it was used against third parties. There is a certain legal agreement that, if the patent is invalidated in the course of pending trial, the case is dismissed. However, the consequences of a patent invalidation on a final judgement differ among the surveyed jurisdictions.

When the patent has been used as a legal instrument to negotiate a license or purchase a patent, in most cases, patent invalidation will not oblige the licensor to repay the licensing fees for the time when the patent was in force. However, does the licensor have the right to ask for post-invalidation royalties. Different jurisdictions give different answers.

Moreover, the patentee has every right to give third parties notice of his exclusive right. This might be done by warning letters. Sending warning letter to a primary infringer may be a customary action before filing a law suit. However, a conflict arises when the patentee sends warning letters to secondary infringers. On the one hand, patent law does not distinguish between primary and secondary infringers. On the other hand, sending warning letter to secondary actors has less justification since secondary infringer will not will to start a legal proceeding against the patentee. They simply switch to alternatives. In such a case, the primary infringer’s reputation and business might be destroyed.

After studying the legal solutions in the surveyed jurisdiction, I came to the opinion that: to a certain extent the alleged infringer should be able to claim back the damages he suffered due to an infringement action which was based on defective patent. In case of a contracts, the licensor should lose his right in claiming post-invalidation royalties. Warning letters against primary infringers should not be actionable, while a no-fault liability should apply when the unjustified warning was sent to secondary infringers, and a per-se prohibition rule should apply for warning the public at large.

Keywords: Patent Law, Subsequent Revocation, Subsequent Invalidation, Infringement, Contracts, Warning Letters

Suggested Citation

Mustafa, Zeinab and Mustafa, Zeinab, Unjustified Patent Enforcement (September 12, 2018). MIPLC Master Thesis Series (2017/18), Available at SSRN: https://ssrn.com/abstract=3417103

Zeinab Mustafa (Contact Author)

Brandstock AG ( email )

Bavariaring 20
Munich, 80336

Independent ( email )

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