The doctrine of assignor estoppel is a doctrine of United States patent law barring a patent's seller (assignor) from attacking the patent's validity in subsequent patent infringement litigation. The doctrine is based on the doctrine of legal estoppel, which prohibits a grantor (typically, of real property) from challenging the validity of his/her/its grant.
In Diamond Scientific Co. v. Ambico, Inc.,[1] the United States Court of Appeals for the Federal Circuit distinguished the policies applicable to assignor estoppel from those applicable to licensee estoppel. It therefore held that the doctrine of Lear, Inc. v. Adkins, which applies to licenses and holds that public policy requires that licensees not be muzzled from challenging the validity of possibly spurious patents, does not apply to assignments.[2]
The UK counterpart to this doctrine is the doctrine of non-derogation from grants. Under this doctrine, as explained in British Leyland Motor Corp. v. Armstrong Patents Co.,[3] a seller of realty or goods is not permitted to take any action (such as bringing an infringement action) that will lessen the value to the buyer of the thing sold. Thus, the owner of copyright in the tailpipe of a motor car, having sold the motor car, may not then bring a copyright infringement action to prevent the aftermarket sale of replacement tailpipes to purchasers of those motor cars. The application of the UK doctrine outside real estate law has been limited subsequently to Leyland, however, to consumer protection contexts.[4]
^848 F.2d 1220 (Fed. Cir. 1988).
^The inconsistency of the Federal Circuit's reasoning and that of the Supreme Court in Lear has been the subject of commentary. See Lara J. Hodgson, (2004) Santa Clara Computer & High Tech.L.J.
^Leyland Archived June 10, 2011, at the Wayback Machine
[1986] A.C. 577, [1986] All E.R. 850 (H.L.)].
^See Canon Kabushiki Kaisha v Green Cartridge Co., [1997] UKPC 19 (30 April 1997), [1997] 3 WLR 13, [1997] AC 728, [1997] FSR 817 ('[O]nce one departs from the case in which the unfairness to the customer and the anticompetitive nature of the monopoly is as plain and obvious as it appeared to the House of Lords in British Leyland, the jurisprudential and economic basis for the doctrine becomes extremely fragile.'). For a more extensive discussion of this issue, see British Leyland Motor Corp v Armstrong Patents Co#Subsequent developments.
The doctrine of assignorestoppel is a doctrine of United States patent law barring a patent's seller (assignor) from attacking the patent's validity...
estop him, as enforcing estoppel would defeat the purpose of the Constitution. Acquiescence Assignorestoppel Collateral estoppel (US) De facto corporation...
Legal estoppel is a principle of law, particularly United States patent law, that an assignor or grantor is not permitted subsequently to deny the validity...
licenses. Courts differ on whether it applies in a copyright context. Assignorestoppel Epstein, Richard A. (2010). "The Disintegration of Intellectual Property...
inventive step. In United States patent law, an equitable estoppel barring a patent's seller (assignor) from attacking the patent's validity if they are found...
comparable to, but somewhat broader than, the doctrine of legal estoppel, assignorestoppel, or estoppel by deed in U.S. law. Under the doctrine of non-derogation...
All elements test Assignorestoppel Continuing patent application Design patent Doctrine of inherency Doctrine of repair and reconstruction Duty of candor...
seller owns, a court may step in and create an easement. Easements by estoppel generally look to any promises not made in writing, any money spent by...
following major features: Must be created by agreement, proof of existence and estoppel. Formed by two or more persons The owners are jointly and severally liable...
Turner [1979] 1 WLR 431 is an English land law case, a case of proprietary estoppel. The husband, was a fairly successful man of commerce and at all material...
to contract formation has been modified by developments in the law of estoppel, misleading conduct, misrepresentation, unjust enrichment, and power of...
putative father, or paternity can be determined by the courts through estoppel over time. Today, when paternity is in dispute or doubt, paternity testing...
authority... is merely a form of estoppel, indeed, it has been termed agency by estoppel and you cannot call in aid an estoppel unless you have three ingredients:...
September 2017. Gottlieb, Glenn M. (July 1977). "Res Judicata and Collateral Estoppel in the Law of Partnership". California Law Review. 65 (4): 863–885. doi:10...
repayment of the debt. Hence, promissory estoppel could circumvent the common law rule of Foakes. Promissory estoppel, however, has been thought to be incapable...
contractual term. Two distinct but related types of estoppel recognised in Canada are promissory estoppel or estoppel by representation, which enables courts to...
health care and retirement, increasing the number of employees an employer assigns to complete the work, and better working conditions. The trade union, through...
person Asking price Assemblage Assignee Assignment Assignment of contract Assignor Assessed value – The value set upon a property for taxation purposes Assessment...
to an assignee except that issues, such as lack of performance, by the assignor may not be a valid defence for the obligor. In the United States, the Federal...
evidence is not permitted, leading to the absence of prosecution history estoppel. While US patent trials are heard by a jury, Canadian trials are heard...
Marbury v. Madison, the second was Dred Scott. For instance, 'collateral estoppel' directs that when a litigant wins in a state court, they cannot sue in...
Wing v Bell [1972] Ch 685, a director's service agreement required him to assign his shares in the company if he was terminated, and he was to receive a...
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