{"id":35907,"date":"2021-04-26T21:24:00","date_gmt":"2021-04-26T21:24:00","guid":{"rendered":"https:\/\/www.dinsmore.com\/?post_type=publications&#038;p=35907"},"modified":"2025-11-21T18:27:28","modified_gmt":"2025-11-21T18:27:28","slug":"assignor-estoppel-soil-of-the-common-law-or-a-strange-state-of-affairs","status":"publish","type":"publications","link":"https:\/\/www.dinsmore.com\/publications\/assignor-estoppel-soil-of-the-common-law-or-a-strange-state-of-affairs\/","title":{"rendered":"Assignor Estoppel: Soil of the Common Law or a Strange State of Affairs?"},"content":{"rendered":"\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/www.dinsmore.com\/wp-content\/uploads\/2021\/04\/Minera-v-Hologic-Banner.jpg\" alt=\"\"\/><\/figure>\n\n\n\n<p>On April 21, 2021, the Supreme Court of the United States heard oral arguments in <em>Minerva Surgical, Inc., v. Hologic, Inc., et al.<\/em>, Case No. 20-440, concerning whether to limit, abolish, or uphold the doctrine of assignor estoppel.<\/p>\n\n\n\n<p>The doctrine of assignor estoppel, generally stated, prevents an inventor who assigns his patent from later challenging its validity.<\/p>\n\n\n\n<p>The parties to the case, as well as the Solicitor General for the United States, argued that the Court should either abolish, limit, or affirm the doctrine of assignor estoppel. Specifically,<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Minerva argued that the Court should either abolish the doctrine or limit it to apply only to <em>issued<\/em> patent claims (as opposed to claims still in prosecution at the time of assignment)<a href=\"#_ftn1\" id=\"_ftnref1\">[1]<\/a>;<\/li>\n\n\n\n<li>Hologic argued that the Court should neither limit nor abolish the doctrine<a href=\"#_ftn2\" id=\"_ftnref2\">[2]<\/a>; and<\/li>\n\n\n\n<li>the Solicitor General argued that the Court should limit the doctrine.<a href=\"#_ftn3\" id=\"_ftnref3\">[3]<\/a><\/li>\n<\/ul>\n\n\n\n<p><strong>Arguments on Abolishing Assignor Estoppel<\/strong><\/p>\n\n\n\n<p>Minerva argued the Court should abolish assignor estoppel primarily because the text of the Patent Act made clear that \u201cinvalidity \u2018shall be\u2019 available as a defense in \u2018any\u2019 action asserting patent infringement.\u201d<a href=\"#_ftn4\" id=\"_ftnref4\">[4]<\/a> Hologic responded by arguing that the Court had affirmed the doctrine of assignor estoppel in <em>Westinghouse Elec. &amp; Mfg. Co. v. Formica Insulation Co.<\/em>, 266 U.S. 342 (1924), and that Congress had then incorporated the Court\u2019s adoption of the doctrine in the Patent Act of 1952.<a href=\"#_ftn5\" id=\"_ftnref5\">[5]<\/a><\/p>\n\n\n\n<p>Minerva replied to Hologic\u2019s use of <em>Westinghouse<\/em> by noting that subsequent Supreme Court decisions\u2014particularly <em>Scott Paper Co. v. Marcalus Manufacturing Co.<\/em>, 326 U.S. 249 (1945), and <em>Lear, Inc. v. Adkins<\/em>, 395 U.S. 653 (1969)\u2014demonstrated that the <em>Westinghouse<\/em> decision had not settled the doctrine of assignor estoppel into law. Specifically, Minerva pointed to a section of the <em>Scott Paper <\/em>decision in which the \u201cCourt wondered out loud the \u2018extent\u2019 to which assignor estoppel \u2018may be deemed to have survived the [<em>Westinghouse<\/em>] decision or to be restricted by it.\u2019\u201d<a href=\"#_ftn6\" id=\"_ftnref6\">[6]<\/a> Minerva argued that the uncertainty created by <em>Scott Paper<\/em> meant that when Congress adopted the Patent Act of 1952, assignor estoppel did <em>not<\/em> form part of the common-law backdrop against which Congress legislated.<a href=\"#_ftn7\" id=\"_ftnref7\">[7]<\/a><\/p>\n\n\n\n<p>When considering the argument to abolish the doctrine, the justices focused on whether <em>Westinghouse <\/em>had, indeed, applied assignor estoppel or had merely recognized it and what, if any, effect <em>Scott Paper <\/em>and <em>Lear<\/em> had on <em>Westinghouse<\/em>\u2019s continuing relevance.<\/p>\n\n\n\n<p>For example, during an exchange with the Solicitor General\u2019s counsel, Justice Sotomayor indicated that the changes in patent litigation since 1924 have undermined <em>Westinghouse<\/em>\u2019s precedential value. After the Solicitor General\u2019s counsel admitted, \u201cIt\u2019s true that claim construction has changed to some degree over time,\u201d Justice Sotomayor said, \u201c[T]hat, in my mind, gives credence to Petitioner\u2019s counsel that maybe the doctrine has lost its utility . . .. [Y]ou\u2019ve just admitted that . . . how you read patents has fundamentally . . . changed.\u201d<a href=\"#_ftn8\" id=\"_ftnref8\">[8]<\/a><\/p>\n\n\n\n<p>Justice Barrett noted \u201cuncertainty in the cases, especially ours.\u201d<\/p>\n\n\n\n<p>During an exchange with Hologic\u2019s counsel, Justice Gorsuch explained his view of the precedent in a way favorable to Minerva:<\/p>\n\n\n\n<p>On the <em>stare decisis<\/em> front, . . as I come at it . . . <em>Westinghouse<\/em> didn\u2019t actually apply the doctrine. It acknowledged its existence and allowed challenges over the scope of the . . . patent.<br><br><em>Scott Paper<\/em> called it a \u201clogical embarrassment.\u201d <em>Lear<\/em> said that <em>Scott <\/em>had undermined the basis for patent estoppel, even more than <em>Westinghouse <\/em>had, so it read <em>Westinghouse<\/em> as undermining the basis for patent estoppel.<br><br>The world has changed greatly since then, as Justice Breyer pointed out . . .. And now we have the Patent Office itself, refusing to apply patent estoppel in . . . IPR proceedings. So the only place left that the doctrine seems to apply is in court.<\/p>\n\n\n\n<p>Isn\u2019t that a strange state of affairs . . . to rest on <em>stare decisis<\/em>?<a href=\"#_ftn9\" id=\"_ftnref9\">[9]<\/a><\/p>\n\n\n\n<p>While difficult to predict how they will decide, the justices seemed generally skeptical of <em>Hologic<\/em>\u2019s reliance on <em>Westinghouse<\/em> as establishing assignor estoppel in the common law against which Congress legislated when creating the Patent Act of 1952.<\/p>\n\n\n\n<p><strong>Arguments on Limiting Assignor Estoppel<\/strong><\/p>\n\n\n\n<p>Minerva argued that if the Court decides not to abolish assignor estoppel, it should limit it to apply only to claims issued at the time of assignment.<a href=\"#_ftn10\" id=\"_ftnref10\">[10]<\/a> Minerva noted that \u201c[a]n assignor makes no representations about not-issued claims[.]\u201d<a href=\"#_ftn11\" id=\"_ftnref11\">[11]<\/a><\/p>\n\n\n\n<p>The Solicitor General recognized that \u201c[t]his Court has never actually applied assignor estoppel in a case before it[.]\u201d<a href=\"#_ftn12\" id=\"_ftnref12\">[12]<\/a> The Solicitor General argued that the Court should limit the doctrine of assignor estoppel to cases in which<\/p>\n\n\n\n<p>the assignor sells patent rights for valuable consideration in an arm\u2019s-length transaction, then either contests the validity of a claim materially identical to a claim issued or pending at the time of the assignment, or otherwise contradicts preassignment representations about the patent\u2019s validity.<a href=\"#_ftn13\" id=\"_ftnref13\">[13]<\/a><\/p>\n\n\n\n<p>Several justices seemed to take a dim view of the Solicitor General\u2019s position. Justice Breyer seemed particularly skeptical of any effort to limit the doctrine, noting at one point, \u201cI can understand abolishing it. I can understand keeping it. But limiting it, I\u2019m finding trouble in finding the right way to do that.\u201d<a href=\"#_ftn14\" id=\"_ftnref14\">[14]<\/a> Justice Barrett expressed concern that the government\u2019s position would lead to inefficiency as courts would need to determine \u201cwhat\u2019s materially identical,\u201d potentially leading to \u201ca battle of the experts.\u201d<a href=\"#_ftn15\" id=\"_ftnref15\">[15]<\/a><\/p>\n\n\n\n<p><strong>Conclusion<\/strong><\/p>\n\n\n\n<p>The justices seemed generally skeptical of the argument that <em>Westinghouse<\/em> had established the doctrine of assignor estoppel sufficiently to form part of the common law that existed when Congress enacted the Patent Act of 1952. This would seem to indicate that at least some of the justices lean in favor of Minerva\u2019s textual argument and abolishing assignor estoppel.<\/p>\n\n\n\n<p>Regardless of whether the Court decides to abolish assignor estoppel, it will not likely lead to a rash of inventor-assignors challenging patents that they had previously assigned. As Minerva\u2019s counsel pointed out, \u201cother state law doctrines such as \u2018equitable estoppel\u2019\u201d would remain to \u201cprotect[] against . . . unscrupulous patentees[.]\u201d<a href=\"#_ftn16\" id=\"_ftnref16\">[16]<\/a> If, however, the Court adopts one of the proposed limitations to the doctrine, it could add additional layers of complexity to both patent-assignment transactions and any subsequent infringement litigation between an assignor and assignee.<\/p>\n\n\n\n<p>If you have any questions, please contact the authors of this article or your Dinsmore attorney.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p><a href=\"#_ftnref1\" id=\"_ftn1\">[1]<\/a> <em>Minerva Surgical, Inc., v. Hologic, Inc., et al.<\/em>, No. 20-440, Brief for Petitioner at 14\u201315(\u201cMinerva Brief\u201d) (Feb. 22, 2021), https:\/\/bit.ly\/3nfF4oV.<\/p>\n\n\n\n<p><a href=\"#_ftnref2\" id=\"_ftn2\">[2]<\/a> <em>Minerva Surgical, Inc., v. Hologic, Inc., et al.<\/em>, No. 20-440, Brief for Respondents at 13\u201315(\u201cHologic Brief\u201d) (Mar. 24, 2021), https:\/\/bit.ly\/3xj6TBg.<\/p>\n\n\n\n<p><a href=\"#_ftnref3\" id=\"_ftn3\">[3]<\/a> <em>Minerva Surgical, Inc., v. Hologic, Inc., et al.<\/em>, No. 20-440, Brief for the United States at 9\u201312(\u201cU.S. Brief\u201d) (Mar. 1, 2021), https:\/\/bit.ly\/32HFsTO.<\/p>\n\n\n\n<p><a href=\"#_ftnref4\" id=\"_ftn4\">[4]<\/a> Minerva Brief at 14 (quoting 35 U.S.C. \u00a7 282(b)).<\/p>\n\n\n\n<p><a href=\"#_ftnref5\" id=\"_ftn5\">[5]<\/a> Hologic Brief at 13\u201314.<\/p>\n\n\n\n<p><a href=\"#_ftnref6\" id=\"_ftn6\">[6]<\/a> <em>Minerva Surgical, Inc., v. Hologic, Inc., et al.<\/em>, No. 20-440, Reply Brief for Petitioner at 3(\u201cMinerva Rely Brief\u201d) (April 7, 2021), https:\/\/bit.ly\/3sMo2A3.<\/p>\n\n\n\n<p><a href=\"#_ftnref7\" id=\"_ftn7\">[7]<\/a> Minerva Reply Brief at 6\u20137 and 10\u201311 (\u201cAssignor estoppel\u2014<em>never <\/em>applied by this Court\u2014has nothing like the historical pedigree of those common-law rules which can be applied wholesale in patent litigation.\u201d).<\/p>\n\n\n\n<p><a href=\"#_ftnref8\" id=\"_ftn8\">[8]<\/a> <em>Minerva Surgical, Inc., v. Hologic, Inc., et al.<\/em>, No. 20-440, Oral Argument Tr. at 47:20\u201348:6(\u201cTranscript\u201d) (Apr. 21, 2021), https:\/\/bit.ly\/3gz2tjL.<\/p>\n\n\n\n<p><a href=\"#_ftnref9\" id=\"_ftn9\">[9]<\/a> <em>Id. <\/em>at 76:23\u201377:24<\/p>\n\n\n\n<p><a href=\"#_ftnref10\" id=\"_ftn10\">[10]<\/a> Minerva Reply Brief at 19.<\/p>\n\n\n\n<p><a href=\"#_ftnref11\" id=\"_ftn11\">[11]<\/a> <em>Id.<\/em><\/p>\n\n\n\n<p><a href=\"#_ftnref12\" id=\"_ftn12\">[12]<\/a> U.S. Brief at 10.<\/p>\n\n\n\n<p><a href=\"#_ftnref13\" id=\"_ftn13\">[13]<\/a> <em>Id. <\/em>at 11.<\/p>\n\n\n\n<p><a href=\"#_ftnref14\" id=\"_ftn14\">[14]<\/a> Transcript at 42:19\u201322.<\/p>\n\n\n\n<p><a href=\"#_ftnref15\" id=\"_ftn15\">[15]<\/a> <em>Id.<\/em> at 58:6\u20139.<\/p>\n\n\n\n<p><a href=\"#_ftnref16\" id=\"_ftn16\">[16]<\/a> Minerva Reply Briefat 18 (quoting <em>SCA Hygiene Prods. Aktiebolag v. First Quality Baby Prods., LLC<\/em>, 137 S. Ct. 954, 967 (2017).<\/p>\n","protected":false},"excerpt":{"rendered":"<p>On April 21, 2021, the Supreme Court of the United States heard oral arguments in Minerva Surgical, Inc., v. Hologic, Inc., et al., Case No. 20-440, concerning whether to limit, abolish, or uphold the doctrine of assignor estoppel. The doctrine of assignor estoppel, generally stated, prevents an inventor who assigns his patent from later challenging\u2026<\/p>\n","protected":false},"author":8,"featured_media":0,"menu_order":0,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"tags":[],"publication-type":[8],"class_list":["post-35907","publications","type-publications","status-publish","format-standard","hentry","publication-type-articles"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v26.5 (Yoast SEO v26.9) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Assignor Estoppel: Soil of the Common Law or a Strange State of Affairs? - Dinsmore &amp; Shohl<\/title>\n<meta name=\"description\" content=\"Assignor Estoppel: Soil of the Common Law or a Strange State of Affairs? 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