VLSI Scores Partial Reversal Against Intel at Federal Circuit: Court Clarifies Binding Effect of Extraterritoriality Stipulations and Scope of Prosecution History Estoppel

The U.S. Court of Appeals for the Federal Circuit issued a precedential opinion on April 14, 2026, reversing in part the District of Delaware’s grant of summary judgment of noninfringement in VLSI Technology LLC v. Intel Corporation (Case No. 24-1772). Chief Judge Moore authored the decision, which delivers a partial win for VLSI while also affirming the district court’s exclusion of two of VLSI’s damages theories. The case has been remanded for further proceedings.

VLSI Technology is a patent licensing entity controlled by Fortress Investment Group, a SoftBank subsidiary. The patent at issue, U.S. Patent No. 8,566,836 (the “’836 patent”), covers methods and apparatus for selecting processor cores in multicore systems based on performance parameters such as processing speed. VLSI alleged that Intel’s processor products infringe that patent, but the district court granted summary judgment of noninfringement on two independent grounds — extraterritoriality and the doctrine of equivalents — that the Federal Circuit has now reversed.

The first reversal concerned the scope of a pretrial stipulation the parties entered before trial. U.S. patent law generally requires that infringing acts occur within the United States: for method claims, all steps must be performed domestically; for apparatus claims, the accused products must be used or sold in the United States. The district court had found that because Intel’s manufacturing and certain product-related activities occur abroad, the accused products lacked a sufficient U.S. nexus to support infringement.

The Federal Circuit disagreed. Before trial, VLSI and Intel had agreed in a written stipulation that 70 percent of Intel’s accused products would be “deemed” to have a United States nexus for purposes of the litigation. The court found this language “plain and unambiguous” and held that the district court erred by effectively disregarding the parties’ own agreement and conducting an independent extraterritoriality analysis. Pretrial stipulations bind both parties and the court; a party cannot walk back a factual concession it bargained for once the litigation reaches a stage where that concession is inconvenient. The court reversed the summary judgment on those products covered by the stipulation.

The second reversal addressed prosecution history estoppel in the doctrine of equivalents (DOE) context. The DOE allows a patent owner to assert infringement even where an accused product does not literally fall within the claim language, provided the differences are insubstantial — that is, the accused element performs substantially the same function, in substantially the same way, to achieve substantially the same result. Prosecution history estoppel limits this doctrine: where a patent applicant narrows a claim through amendment or argument during prosecution, the surrendered subject matter is presumptively off-limits for DOE purposes.

The district court had applied prosecution history estoppel broadly and determined that VLSI’s prosecution history amendments foreclosed its DOE theories on certain apparatus claims. The Federal Circuit reversed that determination. The court found the district court had construed the claims incorrectly by drawing on prosecution history in a way that overstated the scope of the surrender. For the apparatus claims, the correct analysis turns on whether the claimed device is capable of performing the patented function, not whether it necessarily does so in every use — and the district court had applied the wrong standard in that capability analysis.

The Federal Circuit did affirm one aspect of the district court’s ruling: the exclusion of expert testimony from VLSI’s damages witness, Dr. Sullivan. Dr. Sullivan had offered two damages theories — a net present value (NPV) model and a value-per-unit (VPU) model — both of which the district court struck before trial. The Federal Circuit found no abuse of discretion in that ruling and declined to reinstate either damages theory. As a result, while the infringement question now goes back to the district court for further proceedings, VLSI will need to advance a damages case without those two methodologies.

This decision carries two important messages for patent litigation practice. First, the binding force of pretrial stipulations cuts in both directions: they can protect a patent owner’s infringement claims (as VLSI’s stipulation did here) but can equally foreclose a defendant’s defenses if carelessly drafted. Counsel negotiating extraterritoriality stipulations — especially in cases involving products with global manufacturing footprints — must anticipate every downstream use of those agreements before signing. Second, the court’s treatment of prosecution history estoppel reaffirms that the doctrine’s scope is bounded by what was actually surrendered, not by the broadest possible reading of prosecution history. Patent owners facing estoppel arguments should scrutinize both the content and the stated rationale of each prosecution amendment; courts are obligated to assess estoppel with precision, not in a wholesale fashion that erases viable DOE theories.