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Assignor estoppel
open-in-new
<h2 id="examples">Examples</h2> <ul><li>For example, if Tom sold his U.S. patent rights to Jerry, and was sued by Jerry over <a href="/facts/Patent_infringement/7vH9JvMF">infringement of that patent</a> later, Tom is not allowed to challenge the patent's validity because he was the inventor.</li></ul> "Doctrine of assignor estoppel prevents unfairness and injustice of permitting party to sell patent rights and later assert that what he sold is worthless."<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> <ul><li>This doctrine extends to those in "<a href="/facts/Privity/geBHbfck">privity</a>" 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.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a></li></ul> <h2 id="case-law">Case law</h2> <ul><li><i>Westinghouse Elec. & Mfg. Co. v. Formica Insulation Co.</i>, 266 U.S. 342, 45 S.Ct. 117 (1924).</li> <li><i>Diamond Scientific Co. v. Ambico, Inc.</i>, 848 F.2d 1220 (Fed. Cir. 1988), in some circumstances, equity may outweigh the estoppel doctrine.</li> <li><i>Mentor Graphics Corp. v. Quickturn Design Sys., Inc.</i>, 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").</li> <li><i>Shamrock Technologies, Inc. v. Med. Sterilization, Inc.</i>, 903 F.2d 789, 793 (Fed. Cir. 1990) (Holding that assignor estoppel extends to parties in privity with the assignor).</li> <li><i>Minerva Surgical, Inc.</i> v. <i>Hologic, Inc.</i> 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."</li></ul> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Inventor_(patent)/LWvWkI2D">Inventor (patent)</a></li> <li><a href="/facts/Licensee_estoppel/cnsok1Jn">Licensee estoppel</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>848 F.2d 1220 (Fed. Cir. 1988). <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>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. <a href="http://www.accessmylibrary.com/coms2/summary_0286-8976827_ITM" target="_blank">http://www.accessmylibrary.com/coms2/summary_0286-8976827_ITM</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Leyland Archived June 10, 2011, at the Wayback Machine [1986] A.C. 577, [1986] All E.R. 850 (H.L.)]. <a href="http://www.uea.ac.uk/~n045/courses/2004/IIPL/documents/british_leyland.pdf" target="_blank">http://www.uea.ac.uk/~n045/courses/2004/IIPL/documents/british_leyland.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>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. <a href="/wiki/British_Leyland_Motor_Corp_v_Armstrong_Patents_Co#Subsequent_developments" target="_blank">/wiki/British_Leyland_Motor_Corp_v_Armstrong_Patents_Co#Subsequent_developments</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Mentor Graphics Corp. v. Quickturn Design Systems, Inc., 150 F.3d 1374 (Fed. Cir. 1998). <a href="/w/index.php?title=Mentor_Graphics_Corp._v._Quickturn_Design_Systems,_Inc.&action=edit&redlink=1" target="_blank">/w/index.php?title=Mentor_Graphics_Corp._v._Quickturn_Design_Systems,_Inc.&action=edit&redlink=1</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>See AltLaw, Checkpoint Systems, Inc. v. All-Tag Security S.A., 412 F.3d 1331 (Fed. Cir. 2005). <a href="http://altlaw.org/v1/cases/192450" target="_blank">http://altlaw.org/v1/cases/192450</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> </ol>