The District of Delaware local rules prohibit additional briefing on motions beyond the opening, answering, and reply briefs permitted by the rules, and the "citation of subsequent authorities":
Except for the citation of subsequent authorities, no additional papers [beyond the response to a motion and a reply brief] shall be filed absent Court approval.
D. Del. Local Rule 7.1.2(b).
It's clear that the "citation" of subsequent authorities is permitted, but what about substantive argument regarding those new authorities?
Personally, I think the rule is clear, and a proper notice of subsequent authority should include a citation but no argument.
(If the Court had expected argument in a "citation of subsequent authorities," it would probably have set a page limit, rather than leaving it unbounded.)
That said, the Court has sometimes permitted and considered substantive argument in notices of subsequent authority, and such notices can potentially prove highly effective—even when relatively lengthy. Other times, the Court has declined to consider improper notices of subsequent authority or struck argumentative responses thereto. See EIS, Inc. v. Intihealth Ger GmbH, No. 19-1227-GBW, 2023 U.S. Dist. LEXIS 102433, at *4 n.1 (D. Del. June 13, 2023) (declining to consider improper notice of subsequent authority).
Last week, Judge Fallon directed the parties in a case to stop submitting "further letter briefing" after they filed a series of argumentative notices of subsequent authority and corresponding responses. She also clarified that notices of subsequent authority should be limited to a "non-argumentative" cover letter, and that no response is permitted:
ORAL ORDER- re 41 Letter. IT IS ORDERED that no further letter briefing on the motion to dismiss (D.I. 23) will be permitted absent leave of court. District of Delaware Local Rule 7.1.2(b) allows a party to file a notice of subsequent authority. D. Del. LR 7.1.2(b). Such notices should be limited to a non-argumentative cover letter with the subsequent authority attached as an exhibit. Rule 7.1.2(b) does not contemplate the filing of a "response" to a notice of subsequent authority. See Targus Intl LLC v. Victorinox Swiss Army, Inc., C.A. No. 20-464-RGA, 2020 WL 7264199, at *1 n.2 (D. Del. Dec. 10, 2020). The court has the pending fully briefed motion to dismiss under advisement, and the filing of additional argumentative letter briefs does not advance the timely resolution of the motion. The court will issue a Report and Recommendation in due course. Ordered by Judge Sherry R. Fallon on 12/11/2025. (lih) (Entered: 12/11/2025)
Safety Holdings Inc. v. Sentinel Information Systems LLC, C.A. No. 24-1224-RGA, D.I. 42 (D. Del. Dec. 11, 2025).
[Update 2025-12-21: The original version of this post stated that the Court did not later reference the improper notices of subsequent authority in its opinion. However, it did refer to the first argumentative notice. See D.I. 43 at 7 n.5.]
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