Shapiro v. McManus, 577 U.S. 39

After the 2010 Census Maryland enacted a new congressional map; petitioners sued alleging First Amendment political-association injury from partisan gerrymandering and requested a three-judge district court.
The district judge dismissed the complaint under Rule 12(b)(6), concluding petitioners’ allegations could not plausibly state a First Amendment claim, and did not notify the circuit chief judge to convene a three-judge court.
The Fourth Circuit summarily affirmed the dismissal. Petitioners sought certiorari, arguing a single judge lacks authority to dismiss rather than refer cases covered by 28 U.S.C. § 2284(a) to a three-judge court.
Central statutory text: § 2284(a) mandates a three-judge court for actions challenging congressional apportionment; § 2284(b)(1) directs the district judge to notify the chief judge “upon the filing of a request for three judges, unless he determines that three judges are not required.”
The question presented: whether the § 2284(b)(1) clause permits a single district judge to decline convening a three-judge court by dismissing the complaint on the merits (or for being legally insufficient) rather than referring it.

Issue	Plaintiffs' Argument	Defendants' Argument	Held
Whether a district judge may refuse to convene a three-judge court for a § 2284(a) action by dismissing the case instead of referring it	Benisek: § 2284(a)’s mandatory "shall" requires convening three judges; § 2284(b)(1) only lets the judge screen whether the request falls within § 2284(a) before notifying the chief judge	State: the "unless he determines that three judges are not required" clause grants discretion to dismiss under ordinary merits standards (e.g., Rule 12(b)(6))	The Court held § 2284(a) is mandatory; § 2284(b)(1) permits only a limited administrative determination whether the request actually invokes § 2284(a), not a merits dismissal by a single judge.
Whether an "insubstantial" constitutional claim exception permits a single judge to avoid convening three judges	Benisek: claim is not insubstantial and merits three-judge consideration	State: district judge may dismiss claims that are constitutionally insubstantial; Goosby allows avoiding three-judge procedure for insubstantial claims	The Court explained Goosby’s narrow "insubstantial" jurisdictional concept applies only to claims that are "wholly insubstantial, frivolous, or plainly non-existent." Petitioners’ complaint was not in that class; the single judge erred in dismissing rather than referring.

Lexecon Inc. v. Milberg Weiss Bershad Hynes & Lerach, 523 U.S. 26 (statutory "shall" creates mandatory obligation)
National Assn. of Home Builders v. Defenders of Wildlife, 551 U.S. 644 (mandatory statutory language interpreted as non-discretionary)
Goosby v. Osser, 409 U.S. 512 (pre-1976 rule: three-judge requirement not triggered by constitutionally insubstantial claims)
Ex parte Poresky, 290 U.S. 30 (substantial federal question required for jurisdiction absent diversity)
Gonzalez v. Automatic Employees Credit Union, 419 U.S. 90 (three-judge court not required where district court lacks jurisdiction or claim is nonjusticiable)
Bell v. Hood, 327 U.S. 678 (insubstantial/frivolous claims and distinction between jurisdictional insufficiency and failure on the merits)
Ashcroft v. Iqbal, 556 U.S. 662 (pleading standard cited by district court)
Bell Atlantic Corp. v. Twombly, 550 U.S. 544 (pleading standard cited by district court)
Washington v. Confederated Tribes of Colville Reservation, 447 U.S. 134 (constitutional claims not lightly deemed insubstantial)
Vieth v. Jubelirer, 541 U.S. 267 (plurality and Kennedy concurrence on political gerrymandering doctrine)