The doctrine of assignor estoppel is a doctrine of

United States patent law Under United States law, a patent is a right granted to the inventor of a (1) process, machine, article of manufacture, or composition of matter, (2) that is new, useful, and non-obvious. A patent is the right to exclude others, for a limited ...

barring a

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling disclo ...

'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.'', 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 ''Lear, Inc. v. Adkins'', 395 U.S. 653 (1969), is a decision of the U.S. Supreme Court overturning the doctrine of licensee estoppel and holding that public interest considerations require that licensees be free to challenge the validity of poss ...

'', 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. The UK counterpart to this doctrine is the

doctrine of non-derogation from grants The doctrine of non-derogation from grants is a principle of the law of England and Wales. As the House of Lords explained in '' British Leyland Motor Corp. v. Armstrong Patents Co.'', it states that a seller of realty or goods is not permitted to ...

. Under this doctrine, as explained in '' British Leyland Motor Corp. v. Armstrong Patents Co.'', 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.

Examples

* For example, if Tom sold his U.S. patent rights to Jerry, and was sued by Jerry over infringement of that patent later, Tom is not allowed to challenge the patent's validity because he was the inventor. : "Doctrine of assignor estoppel prevents unfairness and injustice of permitting party to sell patent rights and later assert that what he sold is worthless." ''

Mentor Graphics Corp. v. Quickturn Design Systems, Inc. Mentorship is the influence, guidance, or direction given by a mentor. A mentor is someone who teaches or gives help and advice to a less experienced and often younger person. In an organizational setting, a mentor influences the personal and p ...

'', 150 F.3d 1374 (Fed. Cir. 1998). * This doctrine extends to those in " privity" with the assignor. If Tom becomes another company's largest shareholder, and that company is sued by Jerry over patent infringement, that company could very likely be barred from raising patent validity as a defense even if Tom was not personally involved in the infringing process.Se
AltLaw
Checkpoint Systems, Inc. v. All-Tag Security S.A., 412 F.3d 1331 (Fed. Cir. 2005).

Case law

* '' Westinghouse Elec. & Mfg. Co. v. Formica Insulation Co.'', 266 U.S. 342, 45 S.Ct. 117 (1924). * ''

Diamond Scientific Co. v. Ambico, Inc. Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, bu ...

'', 848 F.2d 1220 (Fed. Cir. 1988), in some circumstances, equity may outweigh the estoppel doctrine. * ''Mentor Graphics Corp. v. Quickturn Design Sys., Inc.'', 150 F.3d 1374, 1377-79 (Fed. Cir. 1998) ("Without exceptional circumstances...one who assigns a patent surrenders with that assignment the right to later challenge the validity of the assigned patent"). * ''Shamrock Technologies, Inc. v. Med. Sterilization, Inc.'', 903 F.2d 789, 793 (Fed. Cir. 1990) (Holding that assignor estoppel extends to parties in privity with the assignor). * ''Minerva Surgical, Inc.'' v. ''Hologic, Inc.'' 594. U.S. ___ (2021) re-affirms the principle of assignor estoppel as long as the assignor contradicts "explicit or implicit representations he made in assigning the patent."

References

{{DEFAULTSORT:Assignor Estoppel United States patent law Estoppel

Examples

Case law

See also

References