Intervening Rights Arise Only When Claim Text Is Amended: Marine Polymer v. HemCon

When a patent’s claims change after grant, the public’s position can change too. A business may have made products that did not infringe the original claims but do infringe the new ones. Intervening rights protect such third parties from being penalized for activity that began before the change.

Marine Polymer Technologies, Inc. v. HemCon, Inc. (Fed. Cir. 2012) (en banc) settled when those rights arise. The answer turns on the text of the claims, not on arguments made about them.

Where intervening rights come from

The core statute is 35 U.S.C. § 252, which governs the effect of a reissue. Other provisions borrow it:

• Reexamination: 35 U.S.C. § 307(b) applies intervening rights to amended or new claims that come out of ex parte reexamination.
• Inter partes review: § 318(c) applies them to amended or new claims in an IPR.
• Post-grant review: § 328(c) does the same for PGR.

Section 252 also provides that claims that are “substantially identical” to the original claims continue in effect from the original grant date. Only claims that are not substantially identical can trigger intervening rights.

Two kinds of intervening rights

Type	What it protects	Court discretion
Absolute	Continued use or sale of specific items made, purchased or used before the reissue or certificate	No; it applies as of right
Equitable	Continued manufacture, use or sale, including expansion, where substantial preparation was made before the change	Yes; the court decides what is equitable

Absolute intervening rights attach to the particular things already in existence. Equitable intervening rights reach further, protecting ongoing business activity, but only to the extent and on the terms a court finds equitable.

The Marine Polymer dispute

The patent in Marine Polymer went through ex parte reexamination. The original claim at issue survived without any change to its wording. During reexamination, however, the patent owner made arguments about claim meaning that, the accused infringer contended, effectively narrowed the meaning of the surviving claim.

The accused infringer argued that a claim narrowed in substance by arguments is no longer the same claim and should be treated as amended for purposes of § 307(b). A Federal Circuit panel initially accepted a version of that argument, but the court then reheard the case en banc.

The en banc holding

A majority of the en banc court held that intervening rights under §§ 307(b) and 252 arise only when claims are amended or new claims are added. Arguments made during reexamination that narrow how a claim is understood, without changing its text, do not create intervening rights.

The reasoning rests on the statutory language. Section 307(b) speaks of amended or new claims. A claim whose words are unchanged is not amended, even if the prosecution history now shapes its construction. That history may still matter for claim construction and for prosecution history estoppel, but it does not trigger intervening rights.

Practical consequences for patent owners

The holding gives patent owners a clear line, and with it some strategic considerations:

• Arguing instead of amending. An owner who can overcome a rejection by argument keeps the original claim text and avoids intervening rights. The arguments still become part of the record and can narrow the claim in later claim construction.
• Amendments have a cost. Any substantive amendment in reissue, ex parte reexamination or an AIA trial can open the door to intervening rights, which may cut off past damages and limit future recovery against existing products.
• New dependent claims. Adding a new claim, even a narrow one, is a change that can carry intervening rights. See reissue procedure, advantages and pitfalls.
• AIA trials. In IPR and PGR, amended or substitute claims are subject to the same principle under §§ 318(c) and 328(c). See amending patent claims during inter partes review.

Whether a change to claim text makes a claim “substantially identical” or not is a separate question, decided by comparing the scope of the original and changed claims. Minor clarifying amendments that do not change scope may leave the claim substantially identical.

Key takeaways

• Intervening rights come from 35 U.S.C. § 252 and apply to reexamination (§ 307(b)), IPR (§ 318(c)) and PGR (§ 328(c)).
• Absolute rights protect existing items; equitable rights are discretionary and can protect ongoing business.
• Marine Polymer v. HemCon (Fed. Cir. 2012) (en banc) held that intervening rights arise only from amended or new claims.
• Narrowing arguments without text changes do not create intervening rights, though they may affect claim construction.
• Patent owners weigh the benefits of an amendment against the intervening rights it may create.