opinion: Justice SCALIA delivered the opinion of the Court.
  We consider under what circumstances, if any, a district judge is free to "determin[e] that three judges are not required" for an action "challenging the constitutionality of the apportionment of congressional districts." 28 U.S.C. §§ 2284(a), (b)(1).
  I
  A
  Rare today, three-judge district courts were more common in the decades before 1976, when they were required for various adjudications, including the grant of an "interlocutory or permanent injunction restraining the enforcement, operation or execution of any State statute ... upon the ground of the unconstitutionality of such statute." 28 U.S.C. § 2281 (1970 ed.), repealed, Pub. L. 94-381, § 1, 90 Stat. 1119. See Currie, The Three-Judge District Court in Constitutional Litigation, 32 U. Chi. L. Rev. 1, 3-12 (1964). Decisions of three-judge courts could, then as now, be appealed as of right directly to this Court. 28 U.S.C. § 1253.
  In 1976, Congress substantially curtailed the circumstances under which a three-judge court is required. It was no longer required for the grant of an injunction against state statutes, see Pub. L. 94-381, § 1, 90 Stat. 1119 (repealing 28 U.S.C. § 2281 ), but was mandated for "an action ... challenging the constitutionality of the apportionment of congressional districts or the apportionment of any statewide legislative body." Id., § 3, now codified at 28 U.S.C. § 2284(a).
  Simultaneously, Congress amended the procedures governing three-judge district courts. The prior statute had provided: "The district judge to whom the application for injunction or other relief is presented shall constitute one member of [the three-judge] court. On the filing of the application, he shall immediately notify the chief judge of the circuit, who shall designate two other judges" to serve. 28 U.S.C. § 2284(1) (1970 ed.). The amended statute provides: "Upon the filing of a request for three judges, the judge to whom the request is presented shall, unless he determines that three judges are not required, immediately notify the chief judge of the circuit, who shall designate two other judges" to serve. 28 U.S.C. § 2284(b)(1) (2012 ed.) (emphasis added). The dispute here concerns the scope of the italicized text.
  B
  In response to the 2010 Census, Maryland enacted a statute in October 2011 establishing-or, more pejoratively, gerrymandering-the districts for the State's eight congressional seats. Dissatisfied with the crazy-quilt results, see App. to Pet. for Cert. 23a, petitioners, a bipartisan group of citizens, filed suit pro se in Federal District Court. Their amended complaint alleges, inter alia, that Maryland's redistricting plan burdens their First Amendment right of political association. Petitioners also requested that a three-judge court be convened to hear the case.
  The District Judge, however, thought the claim "not one for which relief can be granted." Benisek v. Mack, 11 F.Supp.3d 516, 526 (D.Md.2014). "[N]othing about the congressional districts at issue in this case affects in any proscribed way [petitioners'] ability to participate in the political debate in any of the Maryland congressional districts in which they might find themselves. They are free to join preexisting political committees, form new ones, or use whatever other means are at their disposal to influence the opinions of their congressional representatives." Ibid. (brackets, ellipsis, and internal quotation marks omitted).
  For that reason, instead of notifying the Chief Judge of the Circuit of the need for a three-judge court, the District Judge dismissed the action. The Fourth Circuit summarily affirmed in an unpublished disposition. Benisek v. Mack, 584 Fed.Appx. 140 (C.A.4 2014). Seeking review in this Court, petitioners pointed out that at least two other Circuits consider it reversible error for a district judge to dismiss a case under § 2284 for failure to state a claim for relief rather than refer it for transfer to a three-judge court. See LaRouche v. Fowler, 152 F.3d 974, 981-983 (C.A.D.C.1998) ; LULAC v. Texas, 113 F.3d 53, 55-56 (C.A.5 1997) (per curiam ). We granted certiorari. Shapiro v. Mack, 576 U.S. ----, 135 S.Ct. 2805, 192 L.Ed.2d 846 (2015).
  II
  Petitioners' sole contention is that the District Judge had no authority to dismiss the case rather than initiate the procedures to convene a three-judge court. Not so, argue respondents; the 1976 addition to § 2284(b)(1) of the clause "unless he determines that three judges are not required" is precisely such a grant of authority. Moreover, say respondents, Congress declined to specify a standard to constrain the exercise of this authority. Choosing, as the District Judge did, the familiar standard for dismissal under Federal Rule of Civil Procedure 12(b)(6) best serves the purposes of a three-judge court, which (in respondents' view) is to protect States from "hasty, imprudent invalidation" of their statutes by rogue district judges acting alone. Brief for Respondents 27.
  Whatever the purposes of a three-judge court may be, respondents' argument needlessly produces a contradiction in the statutory text. That text's initial prescription could not be clearer: "A district court of three judges shall be convened ... when an action is filed challenging the constitutionality of the apportionment of congressional districts...." 28 U.S.C. § 2284(a) (emphasis added). Nobody disputes that the present suit is "an action ... challenging the constitutionality of the apportionment of congressional districts." It follows that the district judge was required to refer the case to a three-judge court, for § 2284(a) admits of no exception, and "the mandatory 'shall' ... normally creates an obligation impervious to judicial discretion." Lexecon Inc. v. Milberg Weiss Bershad Hynes & Lerach, 523 U.S. 26, 35, 118 S.Ct. 956, 140 L.Ed.2d 62 (1998) ; see also National Assn. of Home Builders v. Defenders of Wildlife, 551 U.S. 644, 661-662, 127 S.Ct. 2518, 168 L.Ed.2d 467 (2007) (same).
  The subsequent provision of § 2284(b)(1), that the district judge shall commence the process for appointment of a three-judge panel "unless he determines that three judges are not required," need not and therefore should not be read as a grant of discretion to the district judge to ignore § 2284(a). It is not even framed as a proviso, or an exception from that provision, but rather as an administrative detail that is entirely compatible with § 2284(a). The old § 2284(1) triggered the district judge's duty to refer the matter for the convening of a three-judge court "[o]n the filing of the application" to enjoin an unconstitutional state law. By contrast, the current § 2284(b)(1) triggers the district judge's duty "[u]pon the filing of a request for three judges" (emphasis added). But of course a party may-whether in good faith or bad, through ignorance or hope or malice-file a request for a three-judge court even if the case does not merit one under § 2284(a). Section 2284(b)(1) merely clarifies that a district judge need not unthinkingly initiate the procedures to convene a three-judge court without first examining the allegations in the complaint. In short, all the district judge must "determin[e]" is whether the "request for three judges" is made in a case covered by § 2284(a) -no more, no less.
  That conclusion is bolstered by § 2284(b)(3)'s explicit command that "[a] single judge shall not ... enter judgment on the merits." It would be an odd interpretation that allowed a district judge to do under § 2284(b)(1) what he is forbidden to do under § 2284(b)(3). More likely that Congress intended a three-judge court, and not a single district judge, to enter all final judgments in cases satisfying the criteria of § 2284(a).
  III
  Respondents argue in the alternative that a district judge is not required to refer a case for the convening of a three-judge court if the constitutional claim is (as they assert petitioners' claim to be) "insubstantial." In Goosby v. Osser, 409 U.S. 512, 93 S.Ct. 854, 35 L.Ed.2d 36 (1973), we stated that the filing of a "constitutionally insubstantial" claim did not trigger the three-judge-court requirement under the pre-1976 statutory regime. Id ., at 518, 93 S.Ct. 854. Goosby rested not on an interpretation of statutory text, but on the familiar proposition that "[i]n the absence of diversity of citizenship, it is essential to jurisdiction that a substantial federal question should be presented." Ex parte Poresky, 290 U.S. 30, 31, 54 S.Ct. 3, 78 L.Ed. 152 (1933) (per curiam ) (emphasis added). Absent a substantial federal question, even a single-judge district court lacks jurisdiction, and "[a] three-judge court is not required where the district court itself lacks jurisdiction of the complaint or the complaint is not justiciable in the federal courts." Gonzalez v. Automatic Employees Credit Union, 419 U.S. 90, 100, 95 S.Ct. 289, 42 L.Ed.2d 249 (1974).
  In the present case, however, the District Judge dismissed petitioners' complaint not because he thought he lacked jurisdiction, but because he concluded that the allegations failed to state a claim for relief on the merits, citing Ashcroft v. Iqbal, 556 U.S. 662, 129 S.Ct. 1937, 173 L.Ed.2d 868 (2009), and Bell Atlantic Corp. v. Twombly, 550 U.S. 544, 127 S.Ct. 1955, 167 L.Ed.2d 929 (2007). See 11 F.Supp.3d, at 520. That was in accord with Fourth Circuit precedent, which holds that where the "pleadings do not state a claim, then by definition they are insubstantial and so properly are subject to dismissal by the district court without convening a three-judge court." Duckworth v. State Admin. Bd. of Election Laws, 332 F.3d 769, 772-773 (C.A.4 2003) (emphasis added).
  We think this standard both too demanding and inconsistent with our precedents. "[C]onstitutional claims will not lightly be found insubstantial for purposes of" the three-judge-court statute. Washington v. Confederated Tribes of Colville Reservation, 447 U.S. 134, 147-148, 100 S.Ct. 2069, 65 L.Ed.2d 10 (1980). We have long distinguished between failing to raise a substantial federal question for jurisdictional purposes-which is what Goosby addressed-and failing to state a claim for relief on the merits; only "wholly insubstantial and frivolous" claims implicate the former. Bell v. Hood, 327 U.S. 678, 682-683, 66 S.Ct. 773, 90 L.Ed. 939 (1946) ; see also Hannis Distilling Co. v. Mayor and City Council of Baltimore, 216 U.S. 285, 288, 30 S.Ct. 326, 54 L.Ed. 482 (1910) ("obviously frivolous or plainly insubstantial");
  Bailey v. Patterson, 369 U.S. 31, 33, 82 S.Ct. 549, 7 L.Ed.2d 512 (1962) (per curiam ) ("wholly insubstantial," "legally speaking non-existent," "essentially fictitious"); Steel Co. v. Citizens for Better Environment, 523 U.S. 83, 89, 118 S.Ct. 1003, 140 L.Ed.2d 210 (1998) ("frivolous or immaterial"). Absent such frivolity, "the failure to state a proper cause of action calls for a judgment on the merits and not for a dismissal for want of jurisdiction." Bell, supra, at 682, 66 S.Ct. 773. Consistent with this principle, Goosby clarified that " '[c]onstitutional insubstantiality' for this purpose has been equated with such concepts as 'essentially fictitious,' 'wholly insubstantial,' 'obviously frivolous,' and 'obviously without merit.' " 409 U.S., at 518, 93 S.Ct. 854 (citations omitted). And the adverbs were no mere throwaways; "[t]he limiting words 'wholly' and 'obviously' have cogent legal significance." Ibid.
  Without expressing any view on the merits of petitioners' claim, we believe it easily clears Goosby 's low bar; after all, the amended complaint specifically challenges Maryland's apportionment "along the lines suggested by Justice Kennedy in his concurrence in Vieth [v. Jubelirer, 541 U.S. 267, 124 S.Ct. 1769, 158 L.Ed.2d 546 (2004) ]." App. to Brief in Opposition 44. Although the Vieth plurality thought all political gerrymandering claims nonjusticiable, Justice KENNEDY, concurring in the judgment, surmised that if "a State did impose burdens and restrictions on groups or persons by reason of their views, there would likely be a First Amendment violation, unless the State shows some compelling interest.... Where it is alleged that a gerrymander had the purpose and effect of imposing burdens on a disfavored party and its voters, the First Amendment may offer a sounder and more prudential basis for intervention than does the Equal Protection Clause." Vieth v. Jubelirer, 541 U.S. 267, 315, 124 S.Ct. 1769, 158 L.Ed.2d 546 (2004). Whatever "wholly insubstantial," "obviously frivolous," etc., mean, at a minimum they cannot include a plea for relief based on a legal theory put forward by a Justice of this Court and uncontradicted by the majority in any of our cases. Accordingly, the District Judge should not have dismissed the claim as "constitutionally insubstantial" under Goosby . Perhaps petitioners will ultimately fail on the merits of their suit, but § 2284 entitles them to make their case before a three-judge district court.
  * * *
  The judgment of the Fourth Circuit is reversed, and the case is remanded for further proceedings consistent with this opinion.
  It is so ordered.
choices: attorney general of the United States, or his office specified state board or department of education city, town, township, village, or borough government or governmental unit state commission, board, committee, or authority county government or county governmental unit, except school district court or judicial district state department or agency governmental employee or job applicant female governmental employee or job applicant minority governmental employee or job applicant minority female governmental employee or job applicant not listed among agencies in the first Administrative Action variable retired or former governmental employee U.S. House of Representatives interstate compact judge state legislature, house, or committee local governmental unit other than a county, city, town, township, village, or borough governmental official, or an official of an agency established under an interstate compact state or U.S. supreme court local school district or board of education U.S. Senate U.S. senator foreign nation or instrumentality state or local governmental taxpayer, or executor of the estate of state college or university United States State person accused, indicted, or suspected of crime advertising business or agency agent, fiduciary, trustee, or executor airplane manufacturer, or manufacturer of parts of airplanes airline distributor, importer, or exporter of alcoholic beverages alien, person subject to a denaturalization proceeding, or one whose citizenship is revoked American Medical Association National Railroad Passenger Corp. amusement establishment, or recreational facility arrested person, or pretrial detainee attorney, or person acting as such;includes bar applicant or law student, or law firm or bar association author, copyright holder bank, savings and loan, credit union, investment company bankrupt person or business, or business in reorganization establishment serving liquor by the glass, or package liquor store water transportation, stevedore bookstore, newsstand, printer, bindery, purveyor or distributor of books or magazines brewery, distillery broker, stock exchange, investment or securities firm construction industry bus or motorized passenger transportation vehicle business, corporation buyer, purchaser cable TV car dealer person convicted of crime tangible property, other than real estate, including contraband chemical company child, children, including adopted or illegitimate religious organization, institution, or person private club or facility coal company or coal mine operator computer business or manufacturer, hardware or software consumer, consumer organization creditor, including institution appearing as such; e.g., a finance company person allegedly criminally insane or mentally incompetent to stand trial defendant debtor real estate developer disabled person or disability benefit claimant distributor person subject to selective service, including conscientious objector drug manufacturer druggist, pharmacist, pharmacy employee, or job applicant, including beneficiaries of employer-employee trust agreement, employee health and welfare fund, or multi-employer pension plan electric equipment manufacturer electric or hydroelectric power utility, power cooperative, or gas and electric company eleemosynary institution or person environmental organization employer. If employer's relations with employees are governed by the nature of the employer's business (e.g., railroad, boat), rather than labor law generally, the more specific designation is used in place of Employer. farmer, farm worker, or farm organization father female employee or job applicant female movie, play, pictorial representation, theatrical production, actor, or exhibitor or distributor of fisherman or fishing company food, meat packing, or processing company, stockyard foreign (non-American) nongovernmental entity franchiser franchisee lesbian, gay, bisexual, transexual person or organization person who guarantees another's obligations handicapped individual, or organization of devoted to health organization or person, nursing home, medical clinic or laboratory, chiropractor heir, or beneficiary, or person so claiming to be hospital, medical center husband, or ex-husband involuntarily committed mental patient Indian, including Indian tribe or nation insurance company, or surety inventor, patent assigner, trademark owner or holder investor injured person or legal entity, nonphysically and non-employment related juvenile government contractor holder of a license or permit, or applicant therefor magazine male medical or Medicaid claimant medical supply or manufacturing co. racial or ethnic minority employee or job applicant minority female employee or job applicant manufacturer management, executive officer, or director, of business entity military personnel, or dependent of, including reservist mining company or miner, excluding coal, oil, or pipeline company mother auto manufacturer newspaper, newsletter, journal of opinion, news service radio and television network, except cable tv nonprofit organization or business nonresident nuclear power plant or facility owner, landlord, or claimant to ownership, fee interest, or possession of land as well as chattels shareholders to whom a tender offer is made tender offer oil company, or natural gas producer elderly person, or organization dedicated to the elderly out of state noncriminal defendant political action committee parent or parents parking lot or service patient of a health professional telephone, telecommunications, or telegraph company physician, MD or DO, dentist, or medical society public interest organization physically injured person, including wrongful death, who is not an employee pipe line company package, luggage, container political candidate, activist, committee, party, party member, organization, or elected official indigent, needy, welfare recipient indigent defendant private person prisoner, inmate of penal institution professional organization, business, or person probationer, or parolee protester, demonstrator, picketer or pamphleteer (non-employment related), or non-indigent loiterer public utility publisher, publishing company radio station racial or ethnic minority person or organization protesting racial or ethnic segregation or discrimination racial or ethnic minority student or applicant for admission to an educational institution realtor journalist, columnist, member of the news media resident restaurant, food vendor retarded person, or mental incompetent retired or former employee railroad private school, college, or university seller or vendor shipper, including importer and exporter shopping center, mall spouse, or former spouse stockholder, shareholder, or bondholder retail business or outlet student, or applicant for admission to an educational institution taxpayer or executor of taxpayer's estate, federal only tenant or lessee theater, studio forest products, lumber, or logging company person traveling or wishing to travel abroad, or overseas travel agent trucking company, or motor carrier television station union member unemployed person or unemployment compensation applicant or claimant union, labor organization, or official of veteran voter, prospective voter, elector, or a nonelective official seeking reapportionment or redistricting of legislative districts (POL) wholesale trade wife, or ex-wife witness, or person under subpoena network slave slave-owner bank of the united states timber company u.s. job applicants or employees Army and Air Force Exchange Service Atomic Energy Commission Secretary or administrative unit or personnel of the U.S. Air Force Department or Secretary of Agriculture Alien Property Custodian Secretary or administrative unit or personnel of the U.S. Army Board of Immigration Appeals Bureau of Indian Affairs Bonneville Power Administration Benefits Review Board Civil Aeronautics Board Bureau of the Census Central Intelligence Agency Commodity Futures Trading Commission Department or Secretary of Commerce Comptroller of Currency Consumer Product Safety Commission Civil Rights Commission Civil Service Commission, U.S. Customs Service or Commissioner of Customs Defense Base Closure and REalignment Commission Drug Enforcement Agency Department or Secretary of Defense (and Department or Secretary of War) Department or Secretary of Energy Department or Secretary of the Interior Department of Justice or Attorney General Department or Secretary of State Department or Secretary of Transportation Department or Secretary of Education U.S. Employees' Compensation Commission, or Commissioner Equal Employment Opportunity Commission Environmental Protection Agency or Administrator Federal Aviation Agency or Administration Federal Bureau of Investigation or Director Federal Bureau of Prisons Farm Credit Administration Federal Communications Commission (including a predecessor, Federal Radio Commission) Federal Credit Union Administration Food and Drug Administration Federal Deposit Insurance Corporation Federal Energy Administration Federal Election Commission Federal Energy Regulatory Commission Federal Housing Administration Federal Home Loan Bank Board Federal Labor Relations Authority Federal Maritime Board Federal Maritime Commission Farmers Home Administration Federal Parole Board Federal Power Commission Federal Railroad Administration Federal Reserve Board of Governors Federal Reserve System Federal Savings and Loan Insurance Corporation Federal Trade Commission Federal Works Administration, or Administrator General Accounting Office Comptroller General General Services Administration Department or Secretary of Health, Education and Welfare Department or Secretary of Health and Human Services Department or Secretary of Housing and Urban Development Interstate Commerce Commission Indian Claims Commission Immigration and Naturalization Service, or Director of, or District Director of, or Immigration and Naturalization Enforcement Internal Revenue Service, Collector, Commissioner, or District Director of Information Security Oversight Office Department or Secretary of Labor Loyalty Review Board Legal Services Corporation Merit Systems Protection Board Multistate Tax Commission National Aeronautics and Space Administration Secretary or administrative unit of the U.S. Navy National Credit Union Administration National Endowment for the Arts National Enforcement Commission National Highway Traffic Safety Administration National Labor Relations Board, or regional office or officer National Mediation Board National Railroad Adjustment Board Nuclear Regulatory Commission National Security Agency Office of Economic Opportunity Office of Management and Budget Office of Price Administration, or Price Administrator Office of Personnel Management Occupational Safety and Health Administration Occupational Safety and Health Review Commission Office of Workers' Compensation Programs Patent Office, or Commissioner of, or Board of Appeals of Pay Board (established under the Economic Stabilization Act of 1970) Pension Benefit Guaranty Corporation U.S. Public Health Service Postal Rate Commission Provider Reimbursement Review Board Renegotiation Board Railroad Adjustment Board Railroad Retirement Board Subversive Activities Control Board Small Business Administration Securities and Exchange Commission Social Security Administration or Commissioner Selective Service System Department or Secretary of the Treasury Tennessee Valley Authority United States Forest Service United States Parole Commission Postal Service and Post Office, or Postmaster General, or Postmaster United States Sentencing Commission Veterans' Administration War Production Board Wage Stabilization Board General Land Office of Commissioners Transportation Security Administration Surface Transportation Board U.S. Shipping Board Emergency Fleet Corp. Reconstruction Finance Corp. Department or Secretary of Homeland Security Unidentifiable International Entity