Third Circuit: Arbitrators May Clarify an Ambiguous Merits Award (Even After Issuance) When AAA Rules Delegate Functus Officio Boundaries

1. Introduction

In Prospect Capital Management L.P. v. Stratera Holdings, LLC (3d Cir. Aug. 4, 2026), the Court of Appeals addressed how far an arbitration panel may go in “revising” an interim merits award without violating the functus officio doctrine (the principle that arbitrators generally may not revisit the merits once they have issued a final decision).

The dispute arose from fee-sharing arrangements tied to administrative fees generated by distributions of shares in the Priority Income Fund. The parties—Prospect Capital Management L.P. (administrator calculating fees), and co-owners/participants Stratera Holdings, LLC and Destra Capital Managers LLC—clashed over whether “DRIP” shares (shares issued through a dividend reinvestment program) were included in the base used to calculate fees.

The central issues on appeal were:

  • Whether an “Interim Award” deciding liability (but reserving damages) is “final” enough for functus officio to attach;
  • Whether the panel’s revised interim award was a forbidden merits redetermination or a permissible clarification under the ambiguity exception;
  • Whether Morgan v. Sundance undermines functus officio as arbitration-specific judge-made doctrine; and
  • How adoption of the AAA Rules affects deference to the panel’s application of functus officio limits.

2. Summary of the Opinion

The Third Circuit affirmed confirmation of the final award and rejected Prospect’s attempt to vacate under 9 U.S.C. § 10(a)(4). The court held:

  • The panel’s interim merits determination on liability was sufficiently final for functus officio purposes even though damages were unresolved.
  • The interim award was ambiguous as to whether it covered DRIP shares associated with Provasi (Stratera’s subsidiary) as well as Destra, allowing clarification under the ambiguity exception.
  • Because the parties incorporated AAA Rules—including provisions empowering the arbitrators to interpret and apply the rules governing their powers—the court owed broad deference to the panel’s functus officio analysis.
  • Morgan v. Sundance did not abrogate functus officio; functus officio is a longstanding common-law doctrine specific to arbitration rather than an arbitration-favoring “variant” of a generally applicable federal procedural rule.

3. Analysis

3.1 Precedents Cited

Core Third Circuit functus officio framework

  • Verizon Pa. LLC v. Commc'ns Workers of Am., AFL- CIO, Loc. 1300, 13 F.4th 300 (3d Cir. 2021): The court treated Verizon as the controlling modern articulation of functus officio in the circuit, including: (i) functus officio as a default rule parties may contract around; (ii) the three exceptions; and (iii) the principle that courts do not review arbitration merits and vacatur is limited. Critically, Verizon also rejected the argument that functus officio attaches only when the entire arbitration (liability and remedy) is complete. The panel here used Verizon to hold the interim liability award was “final” for functus officio purposes.
  • Office & Pro. Emps. Int'l Union, Loc. No. 471 v. Brownsville Gen. Hosp., 186 F.3d 326 (3d Cir. 1999): Cited (via Verizon) for the policy rationale: arbitrators lack judicial institutional protections and may be more susceptible to outside influence, supporting a strict rule against reconsideration after issuance.
  • Colonial Penn Ins. Co. v. Omaha Indem. Co., 943 F.2d 327 (3d Cir. 1991): Used to define functus officio’s purpose and narrow the “mistake” exception to clerical/arithmetic errors, preventing parties from relitigating “mistakes in fact” as a backdoor appeal to the arbitrators.
  • La Vale Plaza, Inc. v. R.S. Noonan, Inc., 378 F.2d 569 (3d Cir. 1967): Cited for the proposition that functus officio applies to an arbitrator’s “final award,” anchoring the threshold inquiry into finality.

Deference and “exceeded powers” review

  • Sutter v. Oxford Health Plans LLC, 675 F.3d 215 (3d Cir. 2012), aff'd, 569 U.S. 564 (2013): The Third Circuit relied on Oxford Health Plans for the “arguably construing or applying the contract” standard—if arbitrators are even arguably interpreting the agreement (and here, the incorporated AAA Rules allocating interpretive authority), a court cannot vacate merely because it disagrees.

Ambiguity exception contours (cross-circuit support)

  • Gen. Re Life Corp. v. Lincoln Nat'l Life Ins. Co., 909 F.3d 544 (2d Cir. 2018): Quoted for examples of ambiguity: failure to address a later-arising contingency or susceptibility to more than one interpretation.
  • Sterling China Co. v. Glass, Molders, Pottery, Plastics & Allied Workers Loc. No. 24, 357 F.3d 546 (6th Cir. 2004): Cited through Gen. Re Life as authority defining award ambiguity permitting clarification.

Award vs. opinion; interpreting the dispositive text

  • United Steelworkers of Am. v. Enter. Wheel & Car Corp., 363 U.S. 593 (1960): Used (as in Verizon) to distinguish ambiguity in an opinion from ambiguity in an award. The Third Circuit emphasized that the operative question is whether the award is ambiguous, not whether every line of the accompanying reasoning is perfectly clear.
  • The court also cited decisions from other circuits (e.g., Sixth and Ninth) for the same “opinion ambiguity is not enough” principle, reinforcing that courts should not demand perfectly unambiguous explanatory opinions.

Finality for judicial review vs. finality for functus officio

  • PG Publ., Inc. v. Newspaper Guild of Pittsburgh, 19 F.4th 308 (3d Cir. 2021): Stratera invoked it to import the “complete arbitration rule” (no judicial review until remedy decided). The court rejected the importation: PG Publ. concerns timing of judicial review, while functus officio concerns arbitrator authority and susceptibility to post hoc influence. Verizon controlled the functus officio finality question.

Morgan v. Sundance and survival of functus officio

  • Morgan v. Sundance, 596 U.S. 411 (2022): The Third Circuit read Morgan narrowly: it forbids arbitration-favoring “variants” of generally applicable procedural rules (like waiver). Functus officio, by contrast, is an arbitration-specific common-law doctrine with longstanding pedigree and is not a pro-arbitration tilt over litigation.
  • United States v. Texas, 507 U.S. 529 (1993), and Bayne v. Morris, 68 U.S. 97 (1863): Cited to support the proposition that Congress is presumed not to abrogate long-established common-law principles absent clear statutory purpose, and to demonstrate the historical roots of functus officio predating the FAA.

What was “submitted” and presumed decided

  • Pennsylvania v. Brown, 373 F.2d 771 (3d Cir. 1967) (citing Bingham v. United States, 296 U.S. 211 (1935)): Invoked for the principle that issues clearly presented can be treated as covered by a decision even if not expressly mentioned, supporting the conclusion that the panel’s treatment of DRIP shares could reasonably be read to include categories beyond the narrow wording of the “Holding” paragraph.

3.2 Legal Reasoning

(a) Contracting into AAA Rules shaped both the doctrine and the deference

The parties adopted the AAA Rules. The court highlighted two rules as pivotal: (1) the rule stating that an arbitrator is not empowered to re-determine the merits of any claim already decided (mirroring functus officio), and (2) AAA Rule 9, granting arbitrators power to interpret and apply the rules as they relate to arbitral powers and duties. The Third Circuit treated this as an agreement to let the arbitrators “mark the outer boundaries” of functus officio in the first instance, thus amplifying the already narrow § 10(a)(4) review.

(b) Threshold: the “Interim Award” was final as to liability

Relying on Verizon Pa. LLC v. Commc'ns Workers of Am., AFL- CIO, Loc. 1300, the court held that functus officio can attach to a partial but final merits determination (liability) even if damages remain. Otherwise, arbitrators could be subject to (or perceived as subject to) post-award pressures while remedy issues are pending—the precise concern functus officio addresses.

(c) Morgan did not eliminate functus officio

The court rejected the argument that functus officio is an impermissible arbitration-specific tweak condemned by Morgan v. Sundance. It distinguished between (i) creating arbitration-favoring variants of ordinary federal procedural doctrines and (ii) applying an arbitration-specific common-law doctrine that predates the FAA and is not a “tilt” toward arbitration over litigation.

(d) Ambiguity exception applied: the award was susceptible to more than one interpretation

Prospect argued the “Holding” section was clear: it referenced DRIP shares “for which [Destra] served as sub-wholesaler” and dismissed “all other claims.” The Third Circuit acknowledged the force of that reading.

But the court focused on ambiguity in the operative award instrument as a whole—especially the dispositive “Interim Award” section, which referred to “above-described DRIP Shares,” requiring the reader to consult the preceding discussion to determine what was “above-described.” The opinion’s repeated references to “claimants” and “DRIP shares” generally, combined with the panel’s reliance on Schedule 11.18’s example (which contemplated shares issued prior to May 11, 2018—i.e., Provasi-era shares), made it reasonable to read the interim award as covering both Provasi- and Destra-associated DRIP shares.

Because the award could be read in more than one way, the panel’s revised interim award was treated as a permissible clarification rather than a merits redo. Under the deferential Oxford Health Plans standard, the clarification stood.

3.3 Impact

  • Clarification authority is real when ambiguity is genuine: Parties challenging “revised” awards in the Third Circuit must grapple with whether the original dispositive text, read with the accompanying explanation, leaves interpretive doubt. If it does, arbitrators may clarify without running afoul of functus officio.
  • Interim merits awards can be “final” for functus officio: Even where damages are reserved, arbitrators cannot treat liability determinations as freely revisable; the doctrine may attach issue-by-issue. This strengthens the stability of interim merits rulings while preserving limited clarification for ambiguity.
  • AAA Rules can increase deference on arbitrator power questions: By emphasizing AAA Rule 9’s delegation, the decision signals that institutional-rule incorporation may not only adopt functus officio limits, but also widen the zone of arbitral discretion in defining exceptions and applying them.
  • Morgan’s reach is limited in this context: The opinion positions functus officio as outside Morgan’s anti-arbitration-special-procedure principle, reducing the likelihood of broad doctrinal attacks on functus officio in FAA confirmation/vacatur practice within the circuit.

4. Complex Concepts Simplified

  • Functus officio: Once arbitrators issue a final decision on an issue, they generally lose authority to change it—similar to the idea that the matter is “done.” The doctrine is meant to prevent behind-the-scenes pressure or influence after an award issues.
  • Ambiguity exception: If an award is reasonably open to two meanings, arbitrators may issue a clarification explaining which meaning they intended, so long as they are clarifying—not re-deciding the merits.
  • “Final” for functus officio vs. “final” for judicial review: An award can be final enough to lock in liability (triggering functus officio) even if the overall arbitration is not yet final for court review purposes.
  • FAA § 10(a)(4) (“exceeded powers”): Courts vacate only when arbitrators step outside the authority the parties gave them. Disagreement with interpretation is not enough.
  • Effect of incorporating AAA Rules: Incorporation can function like a contractual “operating system” for the arbitration—including who decides the scope of arbitral authority and how corrections/clarifications work.

5. Conclusion

Prospect Capital Management L.P. v. Stratera Holdings, LLC reinforces a practical Third Circuit rule: an interim merits award can be final as to liability for functus officio, yet still be subject to a narrow clarification power when the award is ambiguous—and where the parties adopted AAA Rules that delegate significant interpretive authority to the arbitrators. The decision also cabins Morgan v. Sundance, preserving functus officio as a valid, longstanding common-law constraint (with exceptions) within FAA § 10(a)(4) review.