Lnu v. Blanche – Do It For The Caselaw

Holding: The court imposed sanctions including monetary penalties and a six-month temporary suspension of practice before the Ninth Circuit against the attorneys for misconduct and lack of candor.
Standard: Duty of candor and professional conduct rules regarding citation accuracy.
Vote: Unanimous decision by the panel.
Practical effect: Attorneys must verify all citations and quotations in filings, disclose the use of generative AI when errors occur, and face potential suspension or monetary sanctions for failing to do so.

The Ninth Circuit imposed sanctions on two attorneys for filing briefs containing fabricated cases and misattributed quotations resulting from generative AI hallucinations, compounded by a failure to disclose the true source of the errors.

Background

Attorneys Mike Singh Sethi and William Rounds filed an opening brief in an immigration appeal containing two nonexistent cases and misattributed quotations from real opinions. When challenged, the attorneys claimed the errors were typographical or copy-paste mistakes and denied the use of generative artificial intelligence. During oral argument, they initially maintained that AI was not used before eventually conceding it was possible. The court found the attorneys violated their duty of candor by failing to transparently disclose the AI origin of the errors.

The court’s reasoning

The court held that procedural and ethical rules apply with equal force regardless of the tool used to draft legal papers. The violation occurred at the point of signing and filing, not at the point of research. The attorneys’ failure to disclose that the errors were AI hallucinations, instead attributing them to innocent mistakes, exacerbated the misconduct and warranted severe discipline.

If an attorney files a brief with cases or quotations that do not exist, or completely misrepresents what a real authority stands for, it generally does not matter if he pulled the hallucination or misrepresentation from the output of an artificial intelligence tool or from his own natural intelligence.

Lnu v. Blanche, 24-4790 (9th Cir. June 3, 2026)

What it means going forward

Attorneys must verify all citations and quotations in filings, disclose the use of generative AI when errors occur, and face potential suspension or monetary sanctions for failing to do so.