Why intervening rights exist
A reissue patent allows a patent owner to correct errors in an issued patent — including errors that resulted in claims that are too narrow (failing to claim the full scope of the invention) or too broad (claiming more than the inventor was entitled to). Broadening reissues must be filed within two years of the original grant (35 U.S.C. § 251). The problem intervening rights address: when a reissue broadens the claims, third parties who were not infringing the original (narrower) claims may suddenly find themselves infringing the new (broader) reissue claims — for activities they undertook in good-faith reliance on the original claim scope. Without intervening rights protection, a patent owner could strategically wait to broaden claims until a competitor had already invested heavily in a product, then retroactively assert infringement. Section 252 prevents this unfairness by protecting those who acted during the gap between original grant and reissue.
The substantially identical test
Not all reissue claims trigger intervening rights. Section 252 provides that a reissue patent shall have the same effect as the original patent except that the reissue claims shall not be effective against those who acted in the intervening period if the reissue claims are 'not substantially identical' to the original claims. The substantially identical test asks whether the scope of the claim changed, not merely whether the words changed. A reissue claim that is narrowed (made more restrictive) is still substantially identical if it covers only a subset of the original claim's scope. A reissue claim that adds new elements, expands definitions, or removes limitations — thereby covering subject matter not covered by the original claim — is not substantially identical, and intervening rights apply. Courts conduct a claim-by-claim analysis; some reissue claims may be substantially identical (no intervening rights) while others are not (intervening rights apply).
Absolute intervening rights: protecting completed transactions
Absolute intervening rights protect specific items — specific articles manufactured, purchased, or put into use — before the reissue patent grants. These rights arise automatically under § 252 without any showing of reliance, harm, or equitable circumstances. If 5,000 units of a product were built and sold before the reissue grant, the purchaser of each of those 5,000 units has an absolute right to use them — even after the reissue, and even if those units fall within the new reissue claim scope. The manufacturer cannot be held liable for past infringement on those units. However, absolute intervening rights protect only the specific pre-reissue items — they do not give the manufacturer ongoing rights to make additional units. Manufacturing even one more unit after the reissue date is potentially infringing (absent equitable intervening rights).
Equitable intervening rights: protecting ongoing activities
Equitable intervening rights are available at the court's discretion to protect substantial preparatory investments made before the reissue grant, even if actual manufacture or sale had not yet occurred. The court balances the equities, considering: the type, amount, and purpose of the pre-reissue investment (tooling, manufacturing setup, contractual commitments, customer deposits); how far the party progressed toward actual manufacture or sale; the degree of reliance on the original claim scope; and whether granting rights would be fair given the circumstances. Courts may grant equitable intervening rights allowing a defendant to: continue manufacturing and selling the same product indefinitely; sell off existing inventory but not manufacture more; manufacture up to a specific quantity; or any other equitable accommodation. Because equitable rights are discretionary, the same facts may produce different outcomes in different courts.
Intervening rights in reexamination and AIA proceedings
Congress extended the intervening rights framework to administrative patent review proceedings. For ex parte reexamination (§ 307(b)) and inter partes reexamination (§ 318(c)), the same substantially identical test applies: if amended claims emerging from reexamination are not substantially identical to the original claims, intervening rights protect pre-reexamination activities. Under the AIA, inter partes review (§ 318(c)) and post-grant review (§ 328(c)) carry the same intervening rights protections when claims are amended through the PTAB motion-to-amend process. The practical implication: when a patent owner amends claims in an IPR or reexamination to avoid invalidating prior art, those amended claims may not be enforceable against accused infringers who acted before the amendment — even though the patent survived review. Defendants in PTAB proceedings who are simultaneously accused of infringement should track any claim amendments and assess whether intervening rights provide a complete defense to the amended claims.
Strategic considerations for patent owners and defendants
For patent owners pursuing reissue: consider whether the expanded claims are necessary before seeking reissue, because broadening triggers intervening rights that limit enforcement against pre-reissue actors; document the prosecution record carefully to support arguments that amended claims are substantially identical to original claims. For defendants: analyze whether reissue or post-PTAB-amendment claims are substantially identical to original claims — this is one of the first questions to answer when an asserted claim was changed in reissue, reexamination, or an AIA proceeding; conduct a timeline analysis to document all pre-reissue manufacture, purchase, use, and significant preparatory investment; preserve documents showing reliance on original claim scope (competitor product teardowns, freedom-to-operate analyses conducted before the reissue). For transactional lawyers: when acquiring patents, investigate whether any claims have been amended in reissue or PTAB proceedings and whether intervening rights could affect enforceability against existing infringers.
Frequently Asked Questions
What are intervening rights in patent law?
Intervening rights (35 U.S.C. § 252) are protections for parties who made, purchased, or used an accused device or method during the period between an original patent grant and a later reissue patent that enlarged or modified the original claims. The doctrine recognizes that when a patent owner amends claims through reissue, third parties who relied on the original (narrower or different) claim scope during the gap period should not face retroactive infringement liability for actions they took when the reissue claims did not yet exist. Section 252 creates two types of intervening rights: (1) Absolute intervening rights — apply automatically to specific items manufactured, purchased, or put to use before the reissue grant; these items cannot be the subject of infringement liability under the reissue claims; (2) Equitable intervening rights — available at the court's discretion to protect substantial investments in preparations to manufacture, use, or sell before the reissue grant, even if the actual manufacturing or use had not yet occurred. Intervening rights apply to reissue patents that contain claims that were 'not substantially identical' to the original patent's claims.
What is the 'substantially identical' test for intervening rights?
Intervening rights only apply when the reissue patent contains claims that are not 'substantially identical' to the claims of the original patent. If the reissue claims are substantially identical to the original claims, no intervening rights arise — the reissue patent can be enforced back to the original grant date. The substantially identical test was developed in the Federal Circuit's jurisprudence: claims are substantially identical if they have the same scope, even if worded differently; if the reissue claims are broader — covering subject matter that the original claims did not — they are not substantially identical and intervening rights apply to the new scope. Claim-by-claim analysis: each reissue claim must be separately analyzed. A reissue patent may contain some claims that are substantially identical to original claims (no intervening rights) and other claims that have been broadened or newly added (intervening rights apply). The patent owner bears the burden of showing that specific reissue claims are substantially identical to original claims to avoid intervening rights.
How do absolute and equitable intervening rights differ?
Absolute intervening rights (§ 252, first sentence of relevant provision): protect specific articles made, purchased, or put in use before the reissue grant. These rights arise automatically — no showing of reliance or investment is required. Example: a manufacturer built 10,000 units of a product before the reissue patent issued; those specific 10,000 units cannot be the subject of infringement under the reissue claims, even if they fall within the new claim scope. But the manufacturer must stop selling or making new units after the reissue date (absent equitable intervening rights). Equitable intervening rights (§ 252, second sentence): protect substantial business preparations made before the reissue that the court in equity determines should be protected. Factors courts consider: the amount of investment in preparing to make or use the product; how far along manufacture or construction was before reissue; the degree of reliance on the original patent's claim scope; and the overall equities. Courts have discretion whether to grant equitable intervening rights and may grant them in full, partially, or not at all. Courts can also grant equitable rights for specific quantities — allowing the party to sell existing inventory but not manufacture more.
Do intervening rights apply to IPR reexamination and PTAB proceedings?
Yes — Congress extended intervening rights principles to ex parte reexamination (35 U.S.C. § 307(b)), inter partes reexamination (§ 318(c)), and, under the AIA, inter partes review (IPR) and post-grant review (PGR) (§§ 318(c) and 328(c)). When claims are amended or new claims are added in reexamination or PTAB proceedings, the same § 252 substantially identical test applies: if the amended claims are not substantially identical to the original claims, intervening rights protect those who made, purchased, or used the product before the reexamination certificate or PTAB final written decision issued. In AIA proceedings, intervening rights apply to claims that emerge from the PTAB proceeding with amendments. Importantly, claims that survive IPR unchanged are not subject to intervening rights — they were never altered, so the substantially identical test is satisfied automatically.
What is the reissue recapture doctrine and how does it interact with intervening rights?
The reissue recapture doctrine (also called prosecution history estoppel in the reissue context) prevents a patent owner from using a reissue application to reclaim subject matter that was deliberately surrendered during original prosecution. If an applicant narrowed claims to overcome a § 103 obviousness rejection (for example), they cannot later broaden those same claims in a reissue to recapture the surrendered scope. The recapture rule and intervening rights interact: recapture doctrine may prevent the reissue claims from being valid at all (if they recapture surrendered subject matter); intervening rights doctrine limits how far back in time valid reissue claims can be enforced. If a reissue claim is invalid under recapture doctrine, the question of intervening rights is moot — the claim cannot be enforced at all. If the claim is valid (it does not recapture), but it is not substantially identical to the original, then intervening rights protect pre-reissue activities. The two doctrines represent different layers of protection against abusive reissue broadening.