T-MOBILE US, INC. v. KAIFI LLC

Federal CircuitAug 28, 2026

Split Score

SplitScore: 45/100

Case Summary

Disposition

Dismissed

The 13th Circuit (Federal Circuit) held that it lacked subject-matter jurisdiction over T-Mobile’s appeal, which concerned the meaning of the phrase “survives the EPR” in a patent-settlement contract with KAIFI. Concluding that the contract dispute did not necessarily raise a substantial question of patent law under Gunn v. Minton, the court transferred the appeal to the Fifth Circuit.

View Full Opinion Document (PDF)

Circuit Split Identified

Legal Issue

Whether a state-law claim that implicates patent issues (e.g., Walker-Process antitrust or contract disputes over re-examination outcomes) ‘arises under’ the patent laws for purposes of 28 U.S.C. §§ 1295(a)(1) and 1338(a), giving the Federal Circuit exclusive appellate jurisdiction.

Circuit Positions

Federal Circuit(this circuit)

Narrow Gunn test – no § 1295/§ 1338 jurisdiction unless the patent question is necessarily raised and substantial; contractual or antitrust claims usually fall outside.

Circuit 5

Broader Gunn test – patent question deemed substantial when the claim could effectively invalidate or render a patent unenforceable, conferring Federal Circuit jurisdiction.

Conflict Summary

The 13th Circuit applies the Gunn v. Minton four-part test strictly, holding that federal-patent jurisdiction exists only when a patent question is necessarily raised and substantial; mere potential impact on a patent’s enforceability is insufficient. The Fifth Circuit, in Xitronix II, found the same statutory language satisfied where the claim could render a still-valid patent unenforceable, viewing that as a substantial federal issue. Thus, the 5th Circuit takes a broader view of what constitutes a ‘substantial’ patent question, while the 13th Circuit takes a narrower view and often transfers such cases.

Parties & Counsel

Parties

Appellant:T-Mobile US, Inc. and T-Mobile USA, Inc.
Appellee:KAIFI LLC

Legal Counsel

Appellant:Gregg Costa, Gibson, Dunn & Crutcher LLP (with Kohl V. Anderson, Jack Disorbo, Nathan R. Curtis, Katherine Q. Dominguez, Josh Krevitt, Andrew W. Robb)
Appellee:Philip J. Warrick, Irell & Manella LLP (with Gregory Albano, Jason Sheasby, Andrew Choung, Jennifer Hayes, Andrew T. Ingram, Grant Martinez, Constance Pfeiffer)