Rule 11 and the AI-Generated Brief: Where the Safe Harbor Helps and Where It Does Not

Short answer: the 21-day safe harbor in Rule 11(c)(2) does not apply when the court acts on its own under Rule 11(c)(3). That is how the AI citation cases have reached sanctions, including the $5,000 penalty in Mata v. Avianca.

Most litigators carry a model of Rule 11 built from fee-shifting practice: opposing counsel serves a motion, you get 21 days to withdraw the paper, the motion is never filed. Accurate, and almost irrelevant to how attorneys have actually been sanctioned for fabricated citations. In those cases nobody served a motion. The court moved first.

Does the Rule 11 safe harbor apply to AI-hallucinated citations?

Only on the motion track. Rule 11(c)(2) opens: “A motion for sanctions must be made separately from any other motion and must describe the specific conduct that allegedly violates Rule 11(b).” The cure period is the next condition in the same paragraph: the motion “must not be filed or be presented to the court if the challenged paper, claim, defense, contention, or denial is withdrawn or appropriately corrected within 21 days after service or within another time the court sets.”

That is a precondition on a private party filing a motion, not a grace period attached to the signing attorney, and it appears nowhere in Rule 11(c)(3), which reads in full: “On its own, the court may order an attorney, law firm, or party to show cause why conduct specifically described in the order has not violated Rule 11(b).” No service requirement. No 21 days. No withdrawal option in the text.

One timing limit does constrain the own-initiative track, and it protects a different interest. Rule 11(c)(5) bars a monetary sanction “on its own, unless it issued the show-cause order under Rule 11(c)(3) before voluntary dismissal or settlement.” That cuts off the court, not the attorney.

What Rule 11(b) certifies when you cite a case

Rule 11(b) attaches the certification to presenting a paper, whether by signing, filing, submitting, or later advocating it. Counsel certifies, on knowledge, information, and belief “formed after an inquiry reasonable under the circumstances,” that legal contentions are “warranted by existing law or by a nonfrivolous argument for extending, modifying, or reversing existing law.” The Second Circuit closed the distance to a fabricated cite in one sentence: “A fake opinion is not ‘existing law’ and citation to a fake opinion does not provide a non-frivolous ground.” Because the certification reaches “later advocating” a paper, defending a brief at argument after learning a cite is fake is itself a presentation.

Two structural points get missed. Exposure is not limited to the signer: under Rule 11(c)(1), “Absent exceptional circumstances, a law firm must be held jointly responsible for a violation committed by its partner, associate, or employee.” And Rule 11 has a hole in it. Rule 11(d): “This rule does not apply to disclosures and discovery requests, responses, objections, and motions under Rules 26 through 37.” A fabricated citation inside a Rule 37 motion to compel falls outside Rule 11 entirely, which pushes the court toward 28 U.S.C. 1927 or its inherent authority.

What the courts actually did: Mata and Park

In Mata v. Avianca, Inc., No. 22-cv-1461 (PKC) (S.D.N.Y. June 22, 2023), Judge Castel wrote that respondents “abandoned their responsibilities when they submitted non-existent judicial opinions with fake quotes and citations created by the artificial intelligence tool ChatGPT.” The proceeding began with the court’s own order to show cause, issued May 4, 2023. The order imposed a “penalty of $5,000” jointly and severally on Peter LoDuca, Steven A. Schwartz, and Levidow, Levidow & Oberman P.C., payable into the Registry of the Court within 14 days, plus letters to the client and to each of the six judges falsely identified as the author of a fabricated opinion. The opinion is not anti-AI: “Technological advances are commonplace and there is nothing inherently improper about using a reliable artificial intelligence tool for assistance.”

In Park v. Kim, No. 22-2057 (2d Cir. Jan. 30, 2024), the panel affirmed the dismissal below and dealt with counsel separately. The reply brief cited a nonexistent decision, “Matter of Bourguignon v. Coordinated Behavioral Health Servs., Inc., 114 A.D.3d 947 (3d Dep’t 2014).” Counsel “failed to determine that her argument was ‘legally tenable,’” and the court ordered: “We therefore REFER Attorney Lee to the Court’s Grievance Panel pursuant to Local Rule 46.2 for further investigation, and for consideration of a referral to the Committee on Admissions and Grievances.”

Note what is absent from both. No Rule 11 motion was served, and no 21-day window ran. The consequences also ran on tracks that should not be blurred: a monetary sanction under Rule 11 in one, a disciplinary referral in the other. Sanctions, discipline, and malpractice are three proceedings with three standards.

Rule table

Provision	Operative language	Source
Certification standard	“formed after an inquiry reasonable under the circumstances”	Fed. R. Civ. P. 11(b)
Legal contentions	“warranted by existing law or by a nonfrivolous argument for extending, modifying, or reversing existing law”	Fed. R. Civ. P. 11(b)(2)
Firm liability	“a law firm must be held jointly responsible for a violation committed by its partner, associate, or employee”	Fed. R. Civ. P. 11(c)(1)
Safe harbor	“must not be filed or be presented to the court if the challenged paper . . . is withdrawn or appropriately corrected within 21 days after service”	Fed. R. Civ. P. 11(c)(2)
Court’s own initiative	“On its own, the court may order an attorney, law firm, or party to show cause why conduct specifically described in the order has not violated Rule 11(b).”	Fed. R. Civ. P. 11(c)(3)
Monetary limit, sua sponte	“on its own, unless it issued the show-cause order under Rule 11(c)(3) before voluntary dismissal or settlement”	Fed. R. Civ. P. 11(c)(5)
Discovery carve-out	“This rule does not apply to disclosures and discovery requests, responses, objections, and motions under Rules 26 through 37.”	Fed. R. Civ. P. 11(d)
Day counting	“exclude the day of the event that triggers the period; count every day, including intermediate Saturdays, Sundays, and legal holidays”	Fed. R. Civ. P. 6(a)(1)
Added time for service	“service is made under Rule 5(b)(2)(C) (mail), (D) (leaving with the clerk), or (F) (other means consented to), 3 days are added”	Fed. R. Civ. P. 6(d)

Drafting-ready text: safe harbor compliance declaration

For the movant, this is the paragraph that decides whether the motion survives a threshold objection. Adapt the bracketed material.

DECLARATION OF [COUNSEL] IN SUPPORT OF MOTION FOR SANCTIONS UNDER FEDERAL RULE OF CIVIL PROCEDURE 11

I, [COUNSEL], declare:

1. I am counsel of record for [PARTY]. I have personal knowledge of the matters stated below and could testify competently to them.

2. On [DATE], [OPPOSING PARTY] filed [DOCUMENT] at ECF No. [NUMBER], citing [NUMBER] authorities that do not exist, identified at paragraphs [NUMBERS] of the accompanying memorandum.

3. On [DATE], I served this motion, with its supporting memorandum and this declaration, on [OPPOSING COUNSEL] by [METHOD]. I did not file it on that date. Service was separate from any other motion, and the motion describes the specific conduct alleged to violate Rule 11(b), as Rule 11(c)(2) requires.

4. More than 21 days have elapsed since service. The period expired on [DATE]. [OPPOSING PARTY] has not withdrawn [DOCUMENT] and has not appropriately corrected it. [Describe any partial correction and why it is not an appropriate correction.]

5. [If served by mail or other consented means] Three days were added under Rule 6(d). The period as extended expired on [DATE].

I declare under penalty of perjury under the laws of the United States of America that the foregoing is true and correct.

Executed on [DATE] at [CITY], [STATE].

_______________________________
[COUNSEL]

Worked example: counting the 21 days

Serve a Rule 11 motion by ECF on Monday, October 5, 2026. Under Rule 6(a)(1) you exclude October 5, then count every day including weekends and intermediate holidays. Day 21 is Monday, October 26, 2026. Columbus Day falls on Monday, October 12, 2026, and extends nothing, because intermediate legal holidays are counted in a day-period. October 26 is not a weekend or holiday, so the cure window closes at the end of that day and the earliest filing date is Tuesday, October 27, 2026.

Change one fact. Serve by mail instead. Rule 6(d) adds 3 days for service under Rule 5(b)(2)(C), (D), or (F), computed after the period would otherwise expire. Expiration moves to Thursday, October 29, 2026, filing to October 30. Electronic service under Rule 5(b)(2)(E) is not on that list and adds nothing.

Now put that against a real posture. If the fabricated citations sit in an opposition to summary judgment and the hearing is 18 days out, the safe harbor eats the entire window and the motion is worthless as a remedy. That is the structural reason these cases arrive through Rule 11(c)(3). Your options are to raise it in the reply, ask the court to act on its own, or both.

Cross-jurisdiction contrast

California. CCP 128.7 tracks the federal certification language, then diverges on the point that matters. Section 128.7(c)(2) lets the court issue an order to show cause on its own motion “unless, within 21 days of service of the order to show cause, the challenged paper, claim, defense, contention, allegation, or denial is withdrawn or appropriately corrected.” California extends a cure period to the court-initiated track that Rule 11(c)(3) does not. Counsel who assume federal practice carries over have it backward.

New York. Part 130 has no cure period at all. Under 22 NYCRR 130-1.1(a) the court “in its discretion, may award to any party or attorney in any civil action” costs and may impose financial sanctions for frivolous conduct, and 130-1.1(c)(1) defines conduct as frivolous where “it is completely without merit in law and cannot be supported by a reasonable argument for an extension, modification or reversal of existing law.”

Bankruptcy. Rule 9011 was amended April 2, 2024, effective December 1, 2024, and subdivision (c) now runs (c)(1) In General, (c)(2) By Motion, (c)(3) By the Court, (c)(4) Nature of a Sanction; Limitations, and (c)(5) Content of a Court Order. The safe harbor sits at 9011(c)(2)(B), and the court’s own track at 9011(c)(3) again carries no cure period. If your form file still cites (c)(1)(A) and (c)(1)(B), update it.

Pre-filing checklist

• Every authority retrieved in full text, not from a summary, and the pin cite read against the proposition.
• Case name, reporter, court, year, and subsequent history confirmed against the opinion itself.
• Quotations compared against the source text, not against the draft.
• Serving a Rule 11 motion: separate from any other motion, describing the specific conduct, served and not filed. Rule 11(c)(2).
• 21 days counted under Rule 6(a)(1), excluding the trigger day, counting intermediate weekends and holidays; 3 days added under Rule 6(d) only for mail, clerk, or other consented service.
• Hearing date checked against the cure window. If the safe harbor outruns the hearing, plan for the Rule 11(c)(3) route.
• If the offending paper is a Rule 26 through 37 filing, confirm the authority is 28 U.S.C. 1927 or inherent authority, not Rule 11. Rule 11(d).
• Assigned judge’s standing order and the district’s local rules checked for any AI certification requirement sitting on top of Rule 11.

Pre-filing citation verification

The Rule 11(b) certification is not satisfied by a tool. It is satisfied by someone pulling each authority in full text and reading the cited page. LegalBriefsUSA runs that verification as a discrete deliverable, on briefs we draft and on briefs your own team drafts, and returns a per-authority log showing what was checked and where. If you have a reply brief going out this week and a stack of cites nobody has personally opened, that is the document to send us.

Related reading: the sanctions record on AI-hallucinated citations, Noland v. Land of the Free and the duty to check the other side’s citations, the CCP 128.7 safe harbor in California, AI disclosure orders in California and New York, and bankruptcy motion practice support.

Authorities cited

Federal Rule of Civil Procedure 11, subdivisions (b), (c)(1) through (c)(6), and (d), and Rule 6, subdivisions (a)(1), (a)(6), and (d), read at law.cornell.edu and law.cornell.edu; Federal Rule of Bankruptcy Procedure 9011, with the amendment note dated April 2, 2024, effective December 1, 2024, read at law.cornell.edu; California Code of Civil Procedure section 128.7, subdivisions (b), (c)(1), and (c)(2), read at california.public.law and confirmed word for word against codes.findlaw.com; 22 NYCRR 130-1.1, subdivisions (a), (b), and (c), read at law.cornell.edu; Mata v. Avianca, Inc., No. 22-cv-1461 (PKC) (S.D.N.Y. June 22, 2023), opinion text read at caselaw.findlaw.com, with the court, date, $5,000 amount, and letter requirements corroborated by a contemporaneous law firm client alert; Park v. Kim, No. 22-2057 (2d Cir. Jan. 30, 2024), opinion text read at caselaw.findlaw.com and at law.justia.com. Omitted for lack of verification today: the Federal Supplement and Federal Reporter page citations for Mata and Park, which neither opinion text displayed; any national count of AI citation decisions; the text of 28 U.S.C. 1927, referenced only as an alternative authority category; and any district local rule or individual judge’s AI certification requirement.

LegalBriefsUSA.com provides drafting and research support to licensed attorneys and law firms. This article is written for attorneys, is not legal advice, and does not create an attorney-client relationship.