The object of the patent system is to reward innovation by providing inventors with a period of exclusive use of their inventions. To this end, a patent includes claims which define the scope of protection given to a patent owner for a predetermined period of time. These patent claims put the public on notice of the patent owner’s property.
The patent system includes a number of mechanisms for changing the claims of a patent after it has issued. Specifically, reissue and reexamination proceedings allow either the patentee or a third party to request that the Patent Office review the claims of an issued patent. During these processes, claims can be cancelled, changed, or left alone. When patent claims are changed, it is possible for the change to adversely affect a party that relied on the public notice function of the patent system. To deal with this risk, courts have applied the doctrine of intervening rights to protect the public from the potential adverse effects of changes to patent claims.
II. BACKGROUND ON REISSUE AND REEXAMINATION
Intervening rights provide a remedy to third parties where their right to use a product or process is affected by a post-issuance change to the scope of a patent’s claims. The two primary mechanisms for changing the claims of an issued patent are reissue and reexamination proceedings.
Chapter 25 of the United States patent laws provides for the amendment and correction of issued patents through “reissue” proceedings in the United States Patent and Trademark Office (PTO). Reissue proceedings are available to a patentee to correct “defects” in the scope of the claims of an issued patent. To apply for reissue, the patentee must assert that the patent is “inoperative or invalid” either due to a defective specification or drawing, or due to the patentee claiming more or less than he or she had a right to claim in the original patent. The patentee must further assert that the “defects” giving rise to the application for reissue arose without any deceptive intent by the reissue applicant. Upon the decision to accept a reissue application, the PTO examines the reissue application in substantially the same manner as it would examine a normal non-provisional patent application.
In light of the language of the reissue statute, a patentee may assert in an application for reissue that his or her original patent is defective because it claims less than the patentee had a right to claim. Thus, patentees in reissue proceedings may enlarge the scope of their original claims, through “broadening reissue applications.” This opportunity, however, is limited. A patentee that desires a broadening reissue application must file within two years of the issue of the original patent. In contrast, “narrowing reissue applications,” which reduce the scope of issued claims, may be filed at any time during the life of the patent.
The PTO recognizes that allowing patentees to change the scope of their original claims may adversely affect the public’s rights relating to the patent invention. Thus, United States patent laws establish that any reissue application functions as an offer to surrender the original patent by the patentee. Upon the grant of a reissue patent, the offer is decreed accepted, and the original patent is surrendered. This leaves only the reissue patent as the basis for any future legal action. Patent laws explicitly set forth additional rules regarding the effect of reissue.
When Congress enacted the Patent Act of 1980, it established a process for reevaluation of the validity of issued patents through “ex parte reexamination” proceedings before the PTO. Reexamination proceedings allow any party to request that the PTO reevaluate the validity of a patent, but this reevaluation is limited to considering of prior art consisting of patents and printed publications. The requester must identify prior art and assert that the identified prior art has a bearing on the patentability of any claim of the patent. Upon any request for reexamination, the Director of the PTO must determine whether the request raises “a substantial new question of patentability” for any claim of the patent. Once a substantial new question of patentability is found, the Director will order a reexamination of the patent.
The scope of reexamination of a patent’s claims is generally limited to questions of patentability arising from those prior art patents or publications identified in the request for reexamination. Notably, and in contrast to reissue proceedings, the claims of the patent cannot be broadened during reexamination proceedings.
Congress supplemented the reexamination process in 1999 by providing for the participation of third parties, via inter partes reexamination of patents. Requests for inter partes reexamination may be filed by any third party in much the same way as described above for ex parte reexamination. During inter partes reexamination, the third party requester is given the right to provide written comments addressing any Office Action issued by the PTO during reexamination or addressing the patentee’s response thereto. The third party requester may also appeal from a final decision of the PTO on patentability of the claims.
III. THE DOCTRINE OF INTERVENING RIGHTS
A. Origins of Intervening Rights
The doctrine of intervening rights is rooted in equity and in the public notice function of patents. Patent claims put the public on notice that the claimed subject matter is excluded from public use for the life of the patent. To the contrary, subject matter disclosed in a patent that is not claimed is considered to be dedicated to the public. In this way, patent claims may be thought of as drawing a line between the subject matter of the patent to which the patentee has exclusive rights, and the subject matter which the patentee has dedicated for public use.
When patent claims are changed (i.e., through reissue or reexamination), the line can become blurred. For example, in broadening reissue patents, subject matter apparently dedicated for public use (by not being covered by the original claims) may be pulled back into the coverage of the claims. This may prejudice a third party, particularly one who acted in reliance on the apparent scope of the original claims. The third party may have expended significant resources on products or processes that before reissue were on the public use side of the line, but after reissue fall inside the line drawn by the claims. Because of situations like this, the doctrine of intervening rights originally was used as an equitable defense for those third parties who relied on the scope of an invention described by the originally issued patent claims. Intervening rights arose as a personal right for a third party, derived from the third party’s pre-reissue activities in reliance on the apparent scope of a patent’s claims.
B. Statutory Basis for Intervening Rights
Congress codified the doctrine of intervening rights in the Patent Act of 1952. Because the codification of intervening rights predated Congress’ establishment of reexamination procedures, the original statute established intervening rights only in reissue applications. Subsequent laws have since expanded these statutory intervening rights to reexamination proceedings.
Section 252 of the Patent Act sets forth two categories of protection, including intervening rights, that arise due to reissue applications. These rights can be separated into protection for pre-reissue activities and rights in post-reissue activities, and are addressed in different paragraphs of the statute.
1. Protection for Pre-Reissue Activities
The first paragraph of section 252 discusses protection for a third party’s activities that occurred prior to the grant of a reissue patent. Such pre-reissue protection is not technically classified as “intervening rights.” Like intervening rights, this protection arises due to the change in the scope of the patent’s claims. However, the protection is considered different because it is guaranteed to all parties by the statute. Thus, unlike intervening rights, the protection provided in the first paragraph of section 252 applies regardless of a party’s pre-reissue activities.
The protection afforded to a patentee by an original patent is surrendered upon the grant of a corresponding reissue patent. Upon grant of the reissue patent, the amended claims are treated as though they were the claims granted on the date the original patent issued. Critical here, however, is that the amended claims are enforceable only for causes “thereafter arising.” Thus, neither the original patent claims nor the reissued claims may be asserted against activities occurring before the grant of the reissue patent. By applying for a reissue patent, the patentee officially surrendered these causes of action, thereby protecting third parties from liability for their pre-reissue activities.
The rule of surrender of the original patent claims is not without exception. Where any of the originally issued claims are substantially identical to any of the claims in the reissued or reexamined patent, the surrender of the original patent does not affect the patentee’s rights to enforce those original claims. The determination of whether claims are substantially identical is left to courts for interpretation.
2. Rights in Post-Reissue Activities
The second paragraph of section 252 provides rights in activities occurring after the grant of a reissue patent. These rights are properly called intervening rights. Intervening rights are divided into two degrees, or types, of intervening rights: absolute intervening rights and equitable intervening rights. This distinction is dictated by the language used in the second paragraph. Absolute intervening rights are provided for in the first sentence, which recites that “[a] reissued patent shall not abridge or affect” certain rights of third parties. Equitable intervening rights are provided for in the second sentence, which recites that “[t]he court before which such matter is in question may provide for [additional third party rights] to the extent and under such terms as the court deems equitable.” The particular rights associated with each type of intervening rights are enumerated in the statute, and have been delineated by Federal Circuit.
As with the protection for pre-reissue activities, the grant of intervening rights is limited by an exception. Section 252 provides for absolute intervening rights unless the third party’s post-reissue activities infringe a valid claim of the reissued patent that was present in the original patent. Like the counterpart exception for pre-reissue activities, the determination of whether a claim was present in the original patent is left to the courts for interpretation.
C. Judicial Applications of Intervening Rights
The application of section 252 to protect pre-reissue and post-reissue activities requires two judicial determinations. First, courts must determine whether the exception to either category of rights applies. Then, if the exception does not apply, courts must determine whether the alleged activities fall within the scope of the protection or rights provided.
1. Exception to Rights
The first determination is whether the claims of the reissued or reexamined patent that are asserted against the third party fall into the exceptions for either category of protections. For pre-reissue activities, this involves the question of whether or not the claims of the reissued or reexamined patent are “substantially identical” to the original claims. For post-reissue activities, this involves the question of whether any valid claim of the reissue patent was “present in the original patent.”
Despite applying to two distinct protections, courts making the first determination have generally interpreted both exceptions as requiring the same thing – that the reissued or reexamined patent claims be “without substantive change” from the original patent claims. According to the courts, reissue claims are without substantive change when their scope is substantially identical to the original claims. Whether the claims are substantively changed depends upon the facts of each case, without reliance on the motives or the correctness of the motives of either the patent examiner or the application. It is a factual determination that requires an analysis of the scope of the original and reissued or reexamined claims in light of the specification, with attention to the references that occasioned the claim amendments, as well as the prosecution history and any other relevant information. Whether an amendment to the claims is substantive is depends on the nature and scope of the amendment.
In line with the origin of intervening rights, courts have not hesitated to find a substantive change to the claims where a patentee expands the scope of their claims in a broadening reissue patent. Notably, courts have found substantive changes even when reissue and reexamination claims underwent narrowing amendments. It appears that any change to the scope of a claim, however small, may be sufficient to remove the statutory exceptions and give rise to protection from infringement.
Courts, generally, have not found a substantive change when the scope of a claim remains the same, even when the form or wording of a claim is altered. Claim amendments that clarify the text or definiteness of the claim are generally viewed as not substantively changing the scope of the claim.
2. Scope of Protection and Rights
If the court determines that a substantial change has been made to the claims, then protection will arise for both pre-reissue and post-reissue activities. The court then need only determine whether the activities of an alleged infringer falls within such protection.
With respect to pre-reissue activities, such a determination is straightforward. Where a substantial change has been made to reissue or reexamination patent claims, the patentee loses all rights and causes of action relating to activities occurring before the grant of reissue or reexamination certificate. With respect to post-reissue activities, the scope of rights provided by absolute intervening rights and equitable intervening rights is different.
i. Absolute Intervening Rights
Absolute intervening rights provide an accused infringer with the absolute right to use or sell a product that was made, used, or purchased before the grant of the reissue patent. Importantly, this absolute right only covers those products that were already in existence at the time of reissue. Absolute intervening rights do not provide a third party with the right to manufacture new patented products. This can be so even if a third party has offered to sell or entered a contract to sell the unmanufactured patented products. As such, the absolute intervening right may be thought of as the right to use or dispose of one’s property free of interference from the reissued or reexamined patent. Absolute intervening rights are guaranteed by the language of the statute, and are not within the discretion of the court.
ii. Equitable Intervening Rights
Equitable intervening rights provide much broader protection than the absolute intervening rights provided by statute. Equitable intervening rights can allow for the continued manufacture, use, or sale of additional products covered by the reissue patent. These rights are available to third parties provided that the parties made, purchased, or used the patented products, or made substantial preparations to make, use, or sell the patented products, before the grant of the reissue patent or reexamination certificate. In addition to patented products, equitable intervening rights may also provide for the continued practice of any process patented by the reissue, provided that process was practiced, or substantial preparation was made to practice, before the grant of the reissue. Thus, equitable rights extend beyond the protection of existing property, and protect continued production of patented products, or continued practice of patented processes.
Unlike absolute intervening rights, courts are given broad discretion on whether to award equitable intervening rights. Section 252 recites that equitable intervening rights may be provided “to the extent and under such terms as the court deems equitable for the protection of investments made or business commenced.”
Courts consider a number of factors in determining whether equitable intervening rights are appropriate to protect third parties. Some of these equitable concerns include (1) whether “substantial preparation” was made by the infringer before reissue; (2) whether the infringer continued manufacturing before reissue on advice of its patent counsel; (3) whether there were existing orders or contracts; (4) whether non-infringing goods can be manufactured from the inventory used to manufacture the infringing product, and the cost of conversion; (5) whether there is a long period of sales and operations before the patent reissued from which no damages can be assed; and (6) whether the alleged infringer has made profits sufficient to recoup its investment. Because this right is equitable in nature, courts may take into account whether or not an alleged infringer has unclean hands before granting equitable intervening rights. Further, even when equitable rights are granted, they may be limited, for example by allowing a third party to make use only of raw materials on hand, or strictly recoup investments.
IV. REISSUE AND REEXAMINATION STRATEGIES
A. Considerations for Pursuing Reissue or Reexamination
There are many instances where a patent holder will find it desirable or necessary to take advantage of reissue or reexamination proceedings. Most importantly, the only mechanism for a patent holder to increase the scope of their claims after the patent has issued is through a broadening reissue application. Reissue proceedings give the patent holder two years after issuance of the original patent to compare the patent’s scope with the state of the art in order to determine whether broader claims are desirable.
Additionally, reissue applications can remedy problems with the claims that cannot be addressed in reexamination proceedings. For example, an issued patent may include claims that have potential problems with definiteness. Before asserting such claims in an infringement scenario, the patent holder may want to clear up any questions relating to the clarity or definiteness of the claims before commencing a litigation. While reexamination requests can only be based on prior art patents and publications, reissue applications can correct any defect in a patent’s claims, whether they are too narrow to protect the patentee’s invention, or are too broad to be valid over the prior art.
Reexamination proceedings may provide patent holders with some advantages. Should a patentee have a question regarding their patent’s validity in light of a newly discovered piece of prior art, ex parte reexamination provides an opportunity to resolve potential invalidity issues. Reexamination provides the patent holder with a means for sharpening and tuning claims to account for any outstanding questions of validity that may arise from new prior art references during the life of the patent.
Further, in ex parte reexamination, a patentee need only argue/negotiate with a patent examiner to prove the validity of the patent’s claims. The patent holder may thereby avoid a prolonged contest against a third party’s advocate in defending the patent against assertions of invalidity.
These advantages are balanced by the different standard of proof used in the PTO. The PTO need not afford a reissue or reexamination application a presumption of validity, though the same patent may be entitled to such a presumption in court.
Reexamination also opens up avenues for third parties to challenge issued patents. A third party may use ex parte reexamination to test the validity of a patent in a limited cost and optionally anonymous manner. A third party can anonymously request that a patent holder defend their patent’s validity in proceedings before the patent office with only a confidential reexamination request and a citation of prior art. Alternatively, a third party may use inter partes reexamination to have a continued role in the process to present arguments to the patent examiner in support of a patent’s invalidity and in response to the patentee’s arguments.
Before undertaking any of these actions, however, it is imperative that a patent holder or third party consider the impact of intervening rights based on the result of the reissue or reexamination proceedings. These considerations are important not merely for the patent holder, but also for the third party faced with possible infringement. Below, we outline the impact of intervening rights on both groups.
B. Intervening Rights Considerations for Patent Holders
The primary consideration practitioners should have in initiating reissue or reexamination proceedings for their clients’ patents relates to amending the patent claims. Causes of action arising under the original patent claims are surrendered if the claims are substantively changed during reissue or reexamination proceedings. Further, certain third parties may obtain intervening rights going forward if a reissue or reexamination results in substantive changes to the claims. There is a risk that any amendment will be deemed a substantive change, regardless of whether it narrows or broadens the claims.
In this light, patentees should first determine whether they want to assert the original patent against any past infringement. Any claims that are substantively amended during reissue or reexamination are unassertable against a third party for past infringement. This means that claims which are broadened to encompass a third party’s past activities cannot be applied against that third party retroactively. This also means that claims which are narrowed during reissue or reexamination cannot be asserted against a third party for past infringement, even if the narrowed claim covered the third party’s activities both before and after the narrowing amendment.
These rights affect decision-making both before and during reissue and reexamination. Where a patentee has questions regarding their patent’s validity, initiating reissue and reexamination contains risks. In court, patents are afforded a presumption of validity. Nonetheless, asserting claims of questionable validity in an infringement suit can open the patent up to challenges to validity. In reissue and reexamination proceedings, questions of validity can be addressed and resolved. Nonetheless, in such proceedings, the PTO will not afford the patent any presumption of validity.
Should a patent enter reissue or reexamination proceedings, patentees must consider their prosecution decisions in light of intervening rights. In some cases, it will be desirable to attempt to overcome rejections by argument rather than amendment. Even where simple, minor amendments could overcome a rejection, those amendments could give rise to intervening rights, and thus be more costly in the long run than a prolonged argument with the examiner.
Finally, in broadening reissue applications, patent holders should consider adding new, broader claims, instead of amending the originally issued claims. New claims that are added to enlarge the scope of the patent will not result in substantive changes to the original patent claims. Thus, the original claims can still be asserted against past infringers. Because the new, broader claims were not present in the original patent, however, they will only be assertable subject to intervening rights.
C. Intervening Rights Considerations for Third Parties
The grant of intervening rights provides a third party with a number of strategies when presented with a potentially troublesome patent. A third party’s strategy typically focuses on causing a substantive change in the patent holders’ claims that either avoids infringement altogether or triggers the doctrine of intervening rights. In this vein, ex parte and inter partes reexamination can be considered as a way to compel patentees to amend their claims.
Where a colorable argument for patent invalidity exists based on one or more prior art references, reexamination can provide a third party with certain advantages over litigation. Notably, a patent examiner in a reexamination interprets patent claims under a different standard than a judge in federal court. While in court, patent claims are afforded a presumption of validity, no such presumption exists at the patent office. During a reexamination, a patent examiner will give both the claims and the prior art their broadest reasonable interpretation in deciding the question of patentability, as if the patent were being examined as an application. Thus, a prior art reference that raises questions of validity could be more effective in reexamination because of the lower standard in the PTO.
A third party may also consider inter partes reexamination to further promote a substantive change to the patent claims. Inter partes reexamination allows a third party to present arguments to the examiner regarding the application of the prior art references to the claims and reply to arguments presented by the patentee.
While a substantive change in a claim is necessary to give rise to intervening rights, third parties should remember that this alone will not give rise to intervening rights. Intervening rights are available only for third parties that took certain affirmative actions prior to the grant of the reissue patent or reexamination certificate. As detailed above, absolute intervening rights extend only to products in existence at the conclusion of reissue or reexamination. Thus, where substantive changes are made during a reissue or reexamination proceeding, third parties will have the absolute right to use or dispose of any existing products they possess at the conclusion of reissue or reexamination.
Third parties should further consider the equitable factors giving rise to equitable intervening rights. Courts have previously been willing to protect substantial preparations made prior to the grant of reissue or reexamined patents. Thus, where substantive changes are made during reissue or reexamination proceedings, third parties may be protected for any preparations made prior to the conclusion or reissue or reexamination. These preparations should nonetheless comply with the requirement of clean hands. Courts may decline to grant any equitable intervening rights where they find an allegedly infringing third party acted with unclean hands. Thus, it is important that third parties avoid willfully infringing a patent, even one undergoing reissue or reexamination. One way to avoid this is by obtaining an opinion of counsel sanctioning the proposed activities, which courts have considered in determining whether to grant equitable intervening rights.
Finally, a third party who properly obtains intervening rights must properly assert them to obtain their benefit. Intervening rights are an affirmative defense to a charge of patent infringement. Thus, an alleged infringer has the burden of proving that substantial changes have been made to the claims. Where substantial changes are established, a third party should have a complete defense to damages for infringement that occurred before the conclusion of reissue or reexamination proceedings, and may have intervening rights going forward.
As reissue and reexamination continue their broad function of correcting the claims of issued patents, patentees should be cognizant of the impact of intervening rights on their use. The doctrine of intervening rights can affect a patent holder’s strategy in correcting the claims of an issued patent. Further, third parties must consider intervening rights in responding to patents they may infringe. By considering the above information regarding intervening rights, practitioners will be able to make more informed decisions regarding their clients’ and competitors’ patents in infringement scenarios.
 Benjamin E. Leace is a shareholder and Andrew J. Koopman is an associate at the law firm RatnerPrestia. This article represents the thoughts and opinions of the authors and not necessarily those of the firm. Nothing in this paper should be construed as legal advice.
 Chapter 25 also provides for the correction of issued patents by disclaimer and by certificates of correction. See 35 U.S.C. §§ 253-256.
 35 U.S.C. § 251.
 Id. See also 36 C.F.R. § 1.175.
 Id. See also 36 C.F.R. § 1.175.
 37 C.F.R. § 1.176
 “Whenever any patent is… deemed wholly or partly inoperative or invalid… by reason of the patentee claiming… less than he had a right to claim in the patent, the Director shall… reissue the patent .” See U.S.C. § 251.
 37 C.F.R. § 1.178.
 See Part III(B), infra (“The Doctrine of Intervening Rights: Statutory Basis for Intervening Rights” (explaining 35 U.S.C. § 252))
 Pub. L. No. 96-517, § 1, 94 Stat. 3015-16 (Dec. 12, 1980) (currently 35 U.S.C. §§ 301-307). For a more detailed discussion of Reexamination proceedings before the United States Patent and Trademark Office, see Benjamin E. Leace and Zachary Fansler, How Reexamination Proceedings at the USPTO Impact the Strategy and Conduct of Patent Litigation, Pennsylvania Bar Institute, Annual Intellectual Property Law Institute, Ch. 24, part 2, p. 763 (2008).
 35 U.S.C. §§ 301-302.
 35 U.S.C. § 303. The Director has broad discretion in determining a substantial new question of patentability exists. See e.g. § 303 (“The existence of a substantial new question of patentability is not precluded by the fact that a patent or printed publication was previously cited by or to the Office or considered by the Office”); In re Swanson, 540 F.3d 1368 (Fed. Cir. 2008) (affirming a determination that a substantial new question exists even though the same question had been adjudicated in district court).
 35 U.S.C. § 304.
 37 C.F.R. § 1.552 (for ex parte reexamination); 37 C.F.R. § 1.906 (for inter partes reexamination).
 Pub. L. No. 106-113, §§ 1000(a)(9), 113 Stat. 1501A-570 (Nov. 29, 1999) (currently 35 U.S.C. §§ 311-318).
 See 35 U.S.C. §§ 311-313.
 35 U.S.C. § 314.
 35 U.S.C. § 315.
 Arnold B. Silverman, To Err is Human – Patent Reissues and the Doctrine of Intervening Rights, 48 J. Pat. Off. Soc’y 696, 696 (1966).
 Id. See also Sontag Chain Stores Co. v. Nat’l Nut Co., 310 U.S. 281, 290 (1940).
 Silverman, supra note 23, at 696.
 See id.
 66 Stat. 808 (July 19, 1952) (currently 35 U.S.C. § 252).
 See 35 U.S.C. § 307(b) (“Any proposed amended or new claim determined to be patentable and incorporated into a patent following a reexamination proceeding will have the same effect as that specified in section 252 of this title for reissued patents…”). Additionally, 35 U.S.C. § 41(c)(2) extends intervening rights to patents that are reinstated after expiration for failure to pay maintenance fees. While the intervening rights statute will be discussed herein with respect to reissue patents (to which it pertains), it will be understood that substantially the same rights apply with respect to reexamination certificates.
 The text of 35 U.S.C. § 252, ¶ 1 recites: The surrender of the original patent shall take effect upon the issue of the reissued patent, and every reissued patent shall have the same effect and operation in law, on the trial of actions for causes thereafter arising, as if the same had been originally granted in such amended form, but in so far as the claims of the original and reissued patents are substantially identical, such surrender shall not affect any action then pending nor abate any cause of action then existing, and the reissued patent, to the extent that its claims are substantially identical with the original patent, shall constitute a continuation thereof and have effect continuously from the date of the original patent.
 See e.g. Fortel Corp. v. Phone-Mate, Inc., 825 F.2d 1577, 1580 (Fed. Cir. 1987) (stating that intervening rights apply solely for activities following reissuance); Kaufman Co., Inc. v. Lantech, Inc., 807 F.2d 970, 976 (Fed. Cir. 1986) (explaining that the rights provided for in the first paragraph of 35 U.S.C. § 252 are not “intervening rights”).
 35 U.S.C. § 252, ¶ 1.
 See Kaufman, supra note 30, at 976; Seattle Box Co., Inc. v. Indus. Crating and Packaging, Inc., 731 F.2d 818, 827 (Fed. Cir. 1984); Voter Verified, Inc. v. Election Sys. & Software, 2010 U.S. Dist. LEXIS 63679, pg. 5-6 (M.D. Fla June 4, 2010).
 35 U.S.C. § 252, ¶ 1.
 See Part III(C), infra (“Judicial Applications of Intervening Rights”).
 The text of 35 U.S.C. § 252, ¶ 2 recites: A reissued patent shall not abridge or affect the right of any person or that person’s successors in business who, prior to the grant of a reissue, made, purchased, offered to sell, or used within the United States, or imported into the United States, anything patented by the reissued patent, to continue the use of, to offer to sell, or to sell to others to be used, offered for sale, or sold, the specific thing so made, purchased, offered for sale, used, or imported unless the making, using, offering for sale, or selling of such thing infringes a valid claim of the reissued patent which was in the original patent. The court before which such matter is in question may provide for the continued manufacture, use, offer for sale, or sale of the thing made, purchased, offered for sale, used, or imported as specified, or for the manufacture, use, offer for sale, or sale in the United States of which substantial preparation was made before the grant of the reissue, and the court may also provide for the continued practice of any process patented by the reissue that is practiced, or for the practice of which substantial preparation was made, before the grant of the reissue, to the extent and under such terms as the court deems equitable for the protection of investments made or business commenced before the grant of the reissue.
 See Kaufman, supra note 30, at 976.
 See e.g. BIC Leisure Prods.., Inc., v. Windsurfing Int’l, Inc., 1 F.3d 1214, 1220 (Fed. Cir. 1993) (citing P.J. Federico, Commentary on the New Patent Act, 35 U.S.C.A. 1, 46 (1954)).
 35 U.S.C. § 252, ¶ 2.
 See Part III(C), infra (“Judicial Applications of Intervening Rights”).
 Seattle Box, supra note 33, at 827-828.
Id. at 830.
 See Slimfold Mfg. Co., Inc. v. Kinkead Indus., Inc., 810 F.2d 1113, 1116 (Fed. Cir. 1987) (regarding the first paragraph of section 252 “[t]he standard applied that of whether a particular change to the claims is substantive”); Kaufman, supra note 30, at 978 (“the cases have consistently construed the second paragraph of § 252 as requiring that a substantive change be made to the claims in a reissue before an infringer is entitled to an intervening right”); Seattle Box, supra note 33, at 827-828 & 831 (holding with respect to the first paragraph that “identical” means “at most, without substantive change,” and holding with respect to the second paragraph that the defense of intervening rights could be raised because the reissue claims were “substantively different”).
 Slimfold, supra note 45, at 1116.
 Bloom Eng’g Co., Inc., v. N. Am. Mfg. Co., Inc., 129 F.3d 1247, 1250 (Fed. Cir. 1997).
 See Fortel Corp., supra note 30, at 1580-81 (holding without analysis that claims were substantive changed where the patentee admitted that reissue claims were “slightly broader”); Seattle Box, supra note 33, at 828 (holding that changing a claimed range from “greater than” to “substantially equal to or greater than” substantively broadened the claim).
 See Bloom Eng’g, supra note 48, at 1250 (affirming finding of a substantive change where applicant added a limitation to specify that a “stream of gas” was “separate from the combustion air stream”); Gen. Elec. Corp. v. Hoescht Celanese Corp., 698 F.Supp. 1181, 1185 (D. Del. 1988) (holding that amending the term “comprising” to recite “consisting essentially of” substantively narrowed the scope of the claims).
 See Bloom Eng’g, supra note 48, at 1250 (holding that amending a dependent claim to be in independent form is not a substantive change to the scope of the dependent claim); see also Nexmed Holdings, Inc. v. Beta Techs., Inc., 2010 U.S. Dist. LEXIS 25245, pg. 30-32 (D. Utah March 17, 2010) (finding no substantive change when an independent claim was amended to include the features of a dependent claim).
 See Tennant Co. v. Hako Minuteman, Inc., 878 F.2d 1413 (Fed. Cir. 1989) (holding that, where claim recited “a second bottom wall section,” amending claimed limitation of “a first wall section” to “a first bottom wall section” did not substantively affect the claim scope, but merely clarified the claim).
 See 35 U.S.C. § 252, ¶ 1; Seattle Box, supra note 33, at 828 (“[patentee] cannot collect damages for any activities performed before its new…claims issued in the reissue patent”).
 BIC Leisure, supra note 38, at 1220-21.
 See Shockley v. Arcan, Inc., 248 F.3d 1349, 1360 (Fed. Cir. 2001) (denying absolute intervening rights to a third party who had offered a number of products for sale but had not manufactured the offered products prior to the grant of a reissue patent).
 See 35 U.S.C. § 252, ¶ 2 (“a reissued patent shall not abridge or affect”).
 BIC Leisure, supra note 38, at 1221.
 35 U.S.C. § 252.
 BIC Leisure, supra note 38, at 1221 (citing 35 U.S.C. § 252).
 Visto Corp. v. Sproqit Tech., Inc., 413 F.Supp. 2d 1073, 1090 (N.D. Cal. 2006) (citing Seattle Box Co. v. Indus. Crating and Packaging, Inc., 756 F.2d 1574 (Fed. Cir. 1985); see also Henrob Ltd. v. Bollhoff Systemtechnick GmbH & Co., 2009 U.S. Dist. LEXIS 89780, pg. 46-47 (E.D. Mich. September 29, 2009).
 See Shockley, supra note 57, at 1361 (denying equitable intervening rights on the grounds that the alleged infringer willfully infringed the original patent); Revolution Eyewear, Inc. v. Aspex Eyewear, Inc., 2008 U.S. Dist. LEXIS 108672, pg. 29 (C.D. Cal. 2008).
 See Seattle Box Co. v. Indus. Crating and Packaging, Inc., 756 F.2d 1574 (Fed. Cir. 1985) (granting equitable intervening rights for third party to dispose of old inventory).
 See 35 U.S.C. § 282.
 See Seattle Box Co., supra note 65.
 See Shockley, supra note 57.
 See InTest Corp. v. Reid-Ashman Mfg., Inc., 66 F.Supp. 2d 576, 582 (D. Del. 1999) (“it is well established, that intervening rights is an affirmative defense”).
 See id.