Federal Circuit IP

Implicit, LLC. v. Sonos, Inc. (with USPTO as intervenor) 

By Caitlin Thireault Published April 15, 2026

Implicit, LLC. v. Sonos, Inc. (with USPTO as intervenor) 

CAFC Opinion No. 2020-1173, 2020-1174, Decided March 9, 2026 

(Taranto, Stoll, Cunningham; Precedential) 

 

Overview:  When is it too late to play the inventorship game?  

Facts/Background 

  • Sonos petitioned for IPR of the ’791 and ’252 patents on §§ 102 and 103 grounds in view of Janevski (US 7,269,338). 
  • Janevski predates the effective filing date of the patents, but Implicit argues that the invention was reduced to practice prior to Janevski, thus it is not prior art (pre-AIA). 
  • Inventors Balassanian and Bradley worked with an engineer, Guy Carpenter, but only  Balassanian and Bradley were named inventors on the application.  
  • Implicit relied on Carpenter’s work to predate the Janevski reference and argued that the named inventors inured the benefit of this work. 
  • PTAB disagreed that there was sufficient evidence that the inventors inured the benefit of Carpenter’s work and found the claims to be anticipated by Janevski. 
  • Two years later, Implicit filed a request to correct inventorship and adds Carpenter as an inventor.  The CAFC remanded to the Board to address whether correcting inventorship had any impact on the final written decision. 
  • The Board found that although correction of inventorship under §256 is generally retroactive, in this case forfeiture, judicial estoppel, and waiver applied.  Implicit appealed.   

Issue:  Does a certificate of correction have a retroactive effect on a final written decision? 

Federal Circuit Analysis –  

  • Review: legal conclusions are de novo and fact findings are substantial evidence. 
  • Board decisions are set aside if arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with the law.  
  • Implicit argues that there is no time limit for correcting inventorship under § 256, and thus equitable doctrines do not apply.  
  • Sonos and the USPTO argue that forfeiture, judicial estoppel, and waiver all apply – cannot raise new antedating arguments when there was an opportunity to raise the arguments earlier on in the proceedings. 
  • Fed. Cir.: Forfeiture can apply notwithstanding the retroactive effect of § 256 and the Board did not abuse its discretion.  Issues of judicial estoppel and waiver were not reached. 

Holding:  Affirmed.   

Takeaways 

  • Although § 256 is generally retroactive, it is not always going to save the day.   
  • Preserve arguments early on in proceedings.