Cervantes v. Bianco
Supreme Court of California · Cal. · California bar guidance
Conduct
Here a sheriff's preliminary brief in an original writ proceeding misquoted, and misstated the holding of, a California Supreme Court precedent on standing.
Consequence
Footnote disapproving the improper use of AI tools, reminding counsel of the duties of competence and candor, and referring the matter to the State Bar; no sanction.
Lesson
Here the California Supreme Court addressed AI-assisted misquotation of its own precedent in a published opinion and sent the matter to the State Bar.
Verified October 1, 2026
- Citation
- Cervantes v. Bianco (Sept. 24, 2026, S295866) ___ Cal.5th ___ [slip opn., p. 8, fn. 7]
- Decided
- September 24, 2026
Summary
Four Riverside County voters petitioned the California Supreme Court directly for a writ of mandate requiring Riverside County Sheriff Chad Bianco to return about 650,000 ballots from the November 4, 2025 special election that his department had seized under search warrants. In his preliminary briefing, Bianco challenged the petitioners' standing "based on misquoted passages from, and an incorrect recitation of our holding in," Common Cause v. Board of Supervisors (1989) 49 Cal.3d 432. The law firm responsible apologized and withdrew the standing argument.
- AI tool:
- Unidentified (the court says the "improper use of artificial intelligence tools" apparently contributed to the error but names no tool)
What did the court warn about?
In footnote 7 of its opinion granting the writ, the court stated: "We disapprove of the improper use of artificial intelligence tools, which apparently contributed to the significant error that occurred here and remind counsel of attorneys' professional duties of competence and candor to the court," citing Rules of Professional Conduct 1.1 and 3.3. It also referred the matter to the State Bar of California "to determine whether discipline is warranted," citing canon 3D(2) of the California Code of Judicial Ethics. The court imposed no monetary or other sanction, and the opinion names neither the law firm nor the attorneys.
Why does Cervantes v. Bianco matter for law firms using AI?
The petitioners, four Riverside County voters, asked the California Supreme Court to order the county sheriff to return roughly 650,000 ballots his department had seized during an investigation of claimed count discrepancies in the November 2025 special election. The court held the seizure unlawful under Elections Code section 15551, subdivision (d), and issued a peremptory writ of mandate directing the sheriff to return the ballots to the registrar of voters.
The AI issue arose in the standing discussion. The sheriff’s preliminary briefing had challenged the petitioners’ standing using misquoted passages from, and an incorrect statement of the holding of, the court’s 1989 decision in Common Cause v. Board of Supervisors. The law firm responsible apologized and withdrew the standing argument. In footnote 7, the court disapproved “the improper use of artificial intelligence tools, which apparently contributed to the significant error,” reminded counsel of the professional duties of competence and candor under Rules 1.1 and 3.3, and referred the matter to the State Bar of California to determine whether discipline is warranted.
The footnote does not identify counsel or the tool, and it does not describe how the error came to light beyond the firm’s apology and withdrawal. Whether and how the referral affects any attorney is a matter for the State Bar; firms with questions about their own obligations may wish to consult a licensed California attorney.
Implications for your firm
Operational steps a firm reading this case may wish to consider documenting. Strategic and rule-application calls belong to your firm's attorneys.
- The error was a misquotation and misstatement of a real precedent, not an invented case. Firms documenting citation-verification procedures may wish to consider whether those procedures check quoted language and stated holdings against the source, not only whether a cited case exists.
- The court tied its reminder to Rules of Professional Conduct 1.1 and 3.3 and made its referral under canon 3D(2), which addresses a judge's response to likely attorney misconduct. Firms with California appellate or writ practice may wish to consider that withdrawing the affected argument did not prevent a published reference to the State Bar, with the application to any particular matter left to counsel.
Sources
Primary sources
- The opinion does not say which law firm or attorney prepared the preliminary briefing, what AI tool was used, or how the court learned that AI contributed to the error; whether the State Bar opened a proceeding on the referral is not public in any source reviewed for this entry.