Clark v. DocuSign (24-1301): Federal Circuit Affirms Patent Unpatentable
Paul C. Clark’s patent covering a system and method for secure communication between domains was found unpatentable, a decision the Federal Circuit affirmed in full. The appeal — resolved after 574 days — signals a definitive end to Clark’s bid to enforce US8695066B1 against DocuSign.
Federal Circuit closes the door on Clark’s secure-domain patent
Paul C. Clark, represented by Cahn & Samuels LLP, filed this appeal at the Court of Appeals for the Federal Circuit on 29 December 2023, challenging a finding that US8695066B1 — a patent covering a system and method for secure communication between domains — is unpatentable. The appellee, DocuSign Co., defended the lower ruling with Fenwick & West LLP. The patent at issue, filed under application number US13/532246, sits at the intersection of network security and electronic transaction infrastructure.
The Federal Circuit issued its order on 25 July 2025, affirming the unpatentability finding in a single-line operative judgment. An affirmance at this level means the appellate panel found no reversible legal or factual error in the decision below. For Clark, the ruling exhausts his appellate options at the Federal Circuit level; for DocuSign, it provides a clean, judicially confirmed basis to operate free of this patent’s claims.
At 574 days, the case duration is broadly consistent with Federal Circuit appeal norms. The terse AFFIRMED order suggests the panel may not have found the appeal to raise novel or close questions — though the public record does not disclose whether a full merits opinion accompanied the order or whether it was disposed of under Rule 36. What drove the original unpatentability finding, and which specific claims were at issue, remains undisclosed in the available record.
Filing to Unpatentable in 574 days
574 days from filing to Federal Circuit disposition — consistent with average CAFC appeal timelines
Federal Circuit affirms: what the ruling means for both parties
Affirmance means no reversible error was found below
When the Federal Circuit issues an AFFIRMED order, it confirms that the lower tribunal’s unpatentability determination contained no reversible legal or factual error. The appellate panel does not re-try the case; it reviews for errors of law de novo and fact findings for substantial evidence. An affirmance on patentability grounds is a final, binding judicial confirmation that the challenged claims do not meet the statutory requirements for patent protection.
Appellate affirmanceUS8695066B1 is judicially confirmed as unpatentable
For Clark, the Federal Circuit’s affirmance is a terminal outcome at this level. The patent’s claims have been adjudged unpatentable, stripping any enforcement or licensing leverage the patent previously represented. Petitioning for en banc rehearing or certiorari to the Supreme Court remains theoretically available but is statistically unlikely to succeed absent a compelling circuit split or constitutional question.
Patent invalidatedDocuSign receives judicial clearance on this patent
DocuSign now holds a Federal Circuit-level affirmance confirming US8695066B1 is unpatentable — the strongest form of patent clearance short of a Supreme Court ruling. This outcome forecloses re-litigation of the same patent claims by Clark, eliminates the need for ongoing design-arounds, and removes a potential licensing cost from DocuSign’s product and IP risk register. The ruling is also citable precedent for any third party seeking to distinguish or challenge related patent claims.
Invalidity confirmedSector-wide clearance on secure cross-domain communication IP
The affirmance of unpatentability for a secure cross-domain communication patent is relevant to any company building electronic signature, identity verification, or multi-domain data exchange products. Competitors and R&D teams working in this space should note that this specific patent family no longer represents an enforcement risk. However, related patents covering overlapping technical approaches may remain active — a freedom-to-operate review of the broader Clark portfolio and adjacent filers is advisable.
FTO implicationsFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Paul C. Clark | Individual | Independent inventor — holder of US8695066B1 covering secure cross-domain communicationSearch in Eureka ↗ |
| Defendant | DocuSign, Co. | Company | DocuSign Co. — electronic agreement platform provider defending unpatentability rulingSearch in Eureka ↗ |
| Plaintiff counsel | Frederick Ngosi Samuels | Attorney | Counsel for Paul C. ClarkSearch in Eureka ↗ |
| Plaintiff counsel | Maurice U. Cahn | Attorney | Counsel for Paul C. ClarkSearch in Eureka ↗ |
| Plaintiff law firm | Cahn & Samuels, LLP | Law Firm | Representing Paul C. ClarkSearch in Eureka ↗ |
| Defendant counsel | Michael John Sacksteder | Attorney | Counsel for DocuSign, Co.Search in Eureka ↗ |
| Defendant counsel | Todd Richard Gregorian | Attorney | Counsel for DocuSign, Co.Search in Eureka ↗ |
| Defendant law firm | Fenwick & West, LLP | Law Firm | Representing DocuSign, Co.Search in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | Court of Appeals for the Federal CircuitSearch in Eureka ↗ |
Official order — verbatim text
The operative judgment — ‘ORDERED AND ADJUDGED: AFFIRMED’ — is a conclusory affirmance with no further elaborated reasoning visible in the public record, consistent with a Federal Circuit Rule 36 summary affirmance, which signals the panel found the case sufficiently clear to decide without a written opinion. For Clark, this forecloses further argument on the merits at this level. For DocuSign, it converts the unpatentability finding into a final appellate judgment, providing the highest-grade patent clearance available short of Supreme Court review.
US8695066B1 — Secure communication between domains
US8695066B1, filed under application number US13/532246, claims a system and method for secure communication between domains — a technical area covering the protocols, architectures, and authentication mechanisms that govern how data moves securely across distinct network or trust boundaries. This class of invention is foundational to electronic agreement platforms, federated identity systems, and any multi-tenant SaaS infrastructure where cross-domain data exchange must be cryptographically secured and access-controlled.
The patent’s assertion against DocuSign — a leading electronic signature and agreement cloud provider — suggests the claimed invention was viewed as potentially reading on core cross-domain security infrastructure deployed in e-signature workflows. The Federal Circuit’s affirmance of unpatentability removes this patent from the enforcement landscape permanently, but companies in adjacent sectors — identity verification, secure API gateways, and digital transaction management — should assess whether related patents in the same inventor’s portfolio or the same CPC subclass present residual risk.
Should you run an FTO against US8695066B1?
Product and R&D teams building secure cross-domain communication systems, electronic signature platforms, or federated identity solutions should note that US8695066B1 has been judicially confirmed as unpatentable — it no longer presents a direct enforcement risk. However, any continuation applications, divisionals, or related patents filed by Paul C. Clark should be independently assessed, as the affirmance applies only to the claims of US8695066B1 as challenged. A targeted FTO review of the broader patent family and closely related CPC classes remains best practice before product launch.
PatSnap Eureka’s FTO Search Agent can rapidly map the patent landscape around secure cross-domain communication technology, identifying active patents, pending applications, and expired rights that may be relevant to your product architecture. Eureka’s AI-driven claim analysis flags potential overlap with your technical specifications and surfaces prior art that informed this and similar invalidation outcomes — giving your legal and engineering teams the intelligence needed to build with confidence.
Run a freedom-to-operate analysis on US8695066B1 to assess your product’s exposure
Run FTO in Eureka →Similar Federal Circuit cases: secure communication & e-signature patents
Explore Federal Circuit appeals involving secure cross-domain communication and electronic signature patents — cases with comparable patentability challenges and CAFC affirmance outcomes.
What this case signals for the electronic signature IP landscape
The Federal Circuit’s affirmance reinforces the patentability bar for secure cross-domain communication methods — with direct relevance to e-signature and identity platform IP strategy.
Unpatentability affirmances raise the bar for similar patent claims
A Federal Circuit-affirmed unpatentability finding on a secure cross-domain communication patent sets a visible precedent. Teams filing or asserting patents in this space should audit claim language against the grounds that invalidated US8695066B1 — whether prior art, obviousness, or Section 101 — to assess exposure of related applications.
DocuSign’s IP clearance is now court-backed, not just procedural
Many invalidity outcomes are settled or dismissed before appellate confirmation. DocuSign’s affirmance at the Federal Circuit level gives its legal and product teams a court-backed basis for operating without this patent’s shadow — a materially stronger position than a district court win alone when licensing negotiations arise.
Clark v DocuSign — key questions answered
The Federal Circuit affirmed the finding that US8695066B1 is unpatentable. The order, issued 25 July 2025, confirms the lower tribunal’s determination with no reversible error identified. The patent, covering a system and method for secure communication between domains, is now judicially confirmed as invalid at the appellate level.
A Rule 36 summary affirmance signals that the Federal Circuit panel found the case sufficiently clear to resolve without a written opinion — suggesting the lower ruling raised no genuinely close legal question. For the patent holder, it is a final adverse judgment at the appellate level, leaving only the low-probability options of en banc rehearing or Supreme Court certiorari.
The patent at issue is US8695066B1, filed under application number US13/532246. It claims a system and method for secure communication between domains — a technology relevant to electronic signature platforms, federated identity systems, and multi-domain network security architectures.
DocuSign now holds a Federal Circuit-confirmed affirmance that US8695066B1 is unpatentable. This eliminates the patent as an enforcement or licensing risk and provides a court-backed basis for continued operation of any product features that may have overlapped with the patent’s claims. It is the strongest patent clearance available at this judicial level.
The public record for this case addresses only US8695066B1. Continuation, divisional, or continuation-in-part applications filed by Paul C. Clark are not covered by this affirmance and may present separate risks. Practitioners and product teams should conduct an independent patent family search and FTO review to identify any co-pending or issued related applications in the secure cross-domain communication space.
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