Unopened Emails. No Agreement to Arbitrate.

The United States Court of Appeals for the Ninth Circuit affirmed the Southern District of California’s denial of Thermo Fisher Scientific’s motion to compel arbitration in Rickes v. Thermo Fisher Scientific, Inc., No. 25‑5138 (Aug. 5, 2026), Not Published.

Scott Rickes, on behalf of himself and similarly situated employees, sued Thermo Fisher under California law, alleging age discrimination and related claims. Thermo Fisher moved to compel arbitration under its Mutual Dispute Resolution Agreement (MDRA), which it distributed to employees by email in 2019.

The district court found that Thermo Fisher failed to prove Rickes had assented to the MDRA and denied the motion to compel arbitration.

The Ninth Circuit reviewed the denial de novo, noting that because the material facts were undisputed, the question of whether an arbitration agreement existed was also reviewed de novo.  Under California law, contract formation requires notice and mutual assent. Assent is determined objectively from outward manifestations and, in some cases, from conduct, but silence alone does not constitute assent.

Writing for the panel (comprising Circuit Judges Kim McLane Wardlaw, John B. Owens, and Ana de Alba), the court reviewed the district court's decision de novo under ordinary California contract formation principles.

The panel underscored several established contract law principles:

Silence Is Not Assent: Quoting Norcia v. Samsung Telecommunications America, LLC, the court reiterated that under California law, "silence alone does not constitute assent."

Affirmative Conduct Required: Citing Sellers v. JustAnswer LLC, the panel pointed out that mutual assent in electronic contexts typically requires an objective, affirmative act—such as clicking an "I Agree" button, checking a box, or actively interacting with the document

Failure to Opt Out Is Insufficient: Simply continuing to work after an unopened or unacknowledged email notice with an opt-out clause does not meet the threshold for mutual assent.