Ninth Circuit Rules AI Agent Liability Falls on the User, Not the Developer
The U.S. Court of Appeals for the Ninth Circuit vacated the preliminary injunction that had blocked Perplexity’s Comet AI shopping agent from operating on Amazon’s platform, issuing the first federal appellate ruling on whether an AI agent constitutes unauthorized access to a third-party site.
The August 4 opinion, written by Circuit Judge Milan D. Smith Jr. in Amazon.com Services LLC v. Perplexity AI Inc., No. 26-1444, held that when an autonomous AI agent accesses a website, it is the user who directed the agent — not the AI company that built it — who is legally performing the access. The case was remanded to the district court for further proceedings consistent with that holding.
What the Ruling Settles
Amazon had sought and obtained a March 2026 preliminary injunction arguing that Perplexity’s Comet agent violated the terms governing access to its platform when it autonomously browsed Amazon listings and executed shopping actions on behalf of users. The district court found Perplexity’s conduct likely constituted unauthorized access.
The Ninth Circuit reversed that reasoning. The appeals court held that agency principles apply: the user who instructs a Comet session to shop on Amazon is the principal; Perplexity is the tool’s maker, not the actor. Liability for unauthorized access tracks the directing party, not the software vendor.
That framing has broad implications. If upheld after remand, it shifts compliance and legal exposure from AI labs to the end users of their agent products — the same structure that governs search engines and web browsers today.
Stakes for the Agent Industry
Perplexity launched Comet as a full computer-use agent capable of browsing, clicking, and transacting across the web on a user’s behalf. Amazon’s injunction, had it stood, would have established a precedent that AI companies bear direct responsibility for every third-party site their agents touch — making it legally hazardous to ship any general-purpose browser-capable agent.
The Ninth Circuit’s framing inverts that. Labs building agents can now argue the legal relationship is between the user and the site, not between the lab and the site. Terms of service enforcement, unauthorized access claims, and platform-blocking disputes would run against the user, not OpenAI, Anthropic, Google, or Perplexity.
Amazon retains its case at the district level. The injunction is lifted, but the underlying legal questions — whether Comet’s access constitutes a terms violation, whether that rises to actionable harm — remain open.
What Comes Next
The ruling is binding in the Ninth Circuit, which covers California, the Pacific Northwest, and several other western states — the jurisdiction that contains most of the AI industry. Other circuits may reach different conclusions as similar disputes work through federal courts.
For AI labs, the decision creates immediate operational relief: agents shipping today are harder to enjoin at the lab level. The longer-term question is whether Congress or the Supreme Court will rationalize the law of AI agent access, or whether a circuit split forces the issue.