(Slip Opinion)              OCTOBER TERM, 2013                                       1

                                       Syllabus

         NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
       being done in connection with this case, at the time the opinion is issued.
       The syllabus constitutes no part of the opinion of the Court but has been
       prepared by the Reporter of Decisions for the convenience of the reader.
       See United States v. Detroit Timber & Lumber Co., 

, 337.


SUPREME COURT OF THE UNITED STATES

                                       Syllabus

 MISSISSIPPI EX REL. HOOD, ATTORNEY GENERAL v.
           AU OPTRONICS CORP. ET AL.

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
                  THE FIFTH CIRCUIT

 No. 12–1036. Argued November 6, 2013—Decided January 14, 2014
Congress enacted the Class Action Fairness Act of 2005 (CAFA) to low-
  er diversity jurisdiction requirements in class actions and, as rele-
  vant here, in mass actions, i.e., civil actions “in which monetary relief
  claims of 100 or more persons are proposed to be tried jointly on the
  ground that the plaintiffs’ claims involve common questions of law or
  fact,” 

. §1332(d)(11)(B)(i). Petitioner Mississippi sued re-
  spondent liquid crystal display (LCD) manufacturers in state court,
  alleging violations of state law and seeking, inter alia, restitution for
  LCD purchases made by itself and its citizens. Respondents sought
  to remove the case to federal court. The District Court held that the
  suit qualified as a mass action under §1332(d)(11)(B)(i), but remand-
  ed the suit to state court on the ground that it fell within CAFA’s
  “general public” exception, §1332(d)(11)(B)(ii)(III). The Fifth Circuit
  reversed, agreeing with the District Court that the suit was a mass
  action but finding the general public exception inapplicable.
Held: Because Mississippi is the only named plaintiff, this suit does not
 constitute a mass action under CAFA. Pp. 5–14.
    (a) Contrary to respondents’ argument, CAFA’s “100 or more per-
 sons” phrase does not encompass unnamed persons who are real par-
 ties in interest to claims brought by named plaintiffs. Congress knew
 how to draft language to that effect when it intended such a meaning,
 see, e.g., §§1332(d)(5)(B), 1332(d)(1)(D). That it did not do so in the
 mass action provision indicates that Congress did not want the provi-
 sion’s numerosity requirement to be satisfied by counting unnamed
 individuals who possess an interest in the suit.
    Respondents’ understanding also cannot be reconciled with the fact
 that the “100 or more persons” are not unspecified individuals with
2        MISSISSIPPI EX REL. HOOD v. AU OPTRONICS CORP.

                                   Syllabus

    no participation in the suit but are the “plaintiffs” subsequently re-
    ferred to in the provision, i.e., the very parties proposing to join their
    claims in a single trial. This is evident in two key ways. First, CAFA
    uses “persons” and “plaintiffs” the same way they are used in Federal
    Rule of Civil Procedure 20, which refers to “persons” as individuals
    who are proposing to join as “plaintiffs” in a single action. Second, it
    is difficult to imagine how the “claims of 100 or more” unnamed indi-
    viduals could be “proposed to be tried jointly on the ground that the
    . . . claims” of some completely different group of named plaintiffs
    “involve common questions of law or fact.”
        Construing “plaintiffs” to include both named and unnamed real
    parties in interest would stretch the meaning of “plaintiff” beyond
    recognition. A “plaintiff” is commonly understood to be a party who
    brings a civil suit in a court of law, not anyone, named or unnamed,
    whom a suit may benefit. Moreover, respondents’ definition would
    also have to apply to the mass action provision’s subsequent refer-
    ence to “plaintiffs” in the phrase “jurisdiction shall exist only over
    those plaintiffs whose claims [exceed $75,000],” §1332(d)(11)(B)(i).
    See Brown v. Gardner, 

, 118. This would result in an
    administrative nightmare that Congress could not possibly have in-
    tended, see Griffin v. Oceanic Contractors, Inc., 

, 575,
    where district courts would have to identify hundreds (or in this case,
    hundreds of thousands) of unnamed parties whose claims are for less
    than $75,000 and then decide how to dispose of their claims. Pp. 5–
    10.
        (b) Statutory context reinforces this Court’s reading of the mass ac-
    tion provision. CAFA provides that once removal occurs, a case shall
    not be transferred to another court “unless a majority of the plaintiffs
    in the action request transfer.” §1332(d)(11)(C)(i). If “plaintiffs” in-
    cluded unnamed parties, it would be surpassingly difficult for a court
    to poll the enormous number of real parties in interest to decide
    whether an action may be transferred. Moreover, respondents’ posi-
    tion that the action here should be removed because it is similar to a
    class action fails to recognize that the mass action provision functions
    largely as a backstop to ensure that CAFA’s relaxed class action ju-
    risdictional rules cannot be evaded by a suit that names a host of
    plaintiffs rather than using the class device. Had Congress wanted
    CAFA to authorize removal of representative actions brought by
    States as sole plaintiffs on respondents’ theory, it would have done so
    through the class action provision, not the mass action provision.
    Pp. 10–11.
        (c) This Court has interpreted the diversity jurisdiction statute to
    require courts in certain contexts to look behind the pleadings to en-
    sure that parties are not improperly creating or destroying diversity
                     Cite as: 571 U. S. ____ (2014)                     3

                                Syllabus

  jurisdiction, see, e.g., Wecker v. National Enameling & Stamping Co.,
  

, 185–186, but Congress did not intend this background
  inquiry to apply to the mass action provision. First, it could make
  sense to incorporate the background inquiry into the mass action
  provision if the inquiry had previously been applied in a similar
  manner. That is not the case here, however, and so any presumption
  that Congress wanted to incorporate the inquiry, if it exists at all,
  would be comparatively weak. Second, even if the background prin-
  ciple had previously been applied in this manner, Congress expressly
  indicated that it did not want the principle to apply to the mass ac-
  tion provision both through the textual indicators described above
  and by prohibiting defendants from joining unnamed individuals to a
  lawsuit in order to turn it into a mass action, §1332(d)(11)(B)(ii)(II).
  Requiring district courts to identify unnamed persons interested in
  the suit would run afoul of that intent. Pp. 11–13.

, reversed and remanded.

  SOTOMAYOR, J., delivered the opinion for a unanimous Court.
                        Cite as: 571 U. S. ____ (2014)                              1

                             Opinion of the Court

     NOTICE: This opinion is subject to formal revision before publication in the
     preliminary print of the United States Reports. Readers are requested to
     notify the Reporter of Decisions, Supreme Court of the United States, Wash-
     ington, D. C. 20543, of any typographical or other formal errors, in order
     that corrections may be made before the preliminary print goes to press.


SUPREME COURT OF THE UNITED STATES
                                   _________________

                                   No. 12–1036
                                   _________________


      MISSISSIPPI EX REL. JIM HOOD, ATTORNEY 

      GENERAL, PETITIONER v. AU OPTRONICS 

               CORPORATION ET AL. 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

            APPEALS FOR THE FIFTH CIRCUIT

                               [January 14, 2014]


   JUSTICE SOTOMAYOR delivered the opinion of the Court.
   Under the Class Action Fairness Act of 2005 (CAFA or
Act), defendants in civil suits may remove “mass actions”
from state to federal court. CAFA defines a “mass action”
as “any civil action . . . in which monetary relief claims of
100 or more persons are proposed to be tried jointly on the
ground that the plaintiffs’ claims involve common ques-
tions of law or fact.” 

. §1332(d)(11)(B)(i). The
question presented is whether a suit filed by a State as the
sole plaintiff constitutes a “mass action” under CAFA
where it includes a claim for restitution based on injuries
suffered by the State’s citizens. We hold that it does not.
According to CAFA’s plain text, a “mass action” must
involve monetary claims brought by 100 or more persons
who propose to try those claims jointly as named plain-
tiffs. Because the State of Mississippi is the only named
plaintiff in the instant action, the case must be remanded
to state court.
2     MISSISSIPPI EX REL. HOOD v. AU OPTRONICS CORP.

                     Opinion of the Court

                               I

                              A

   Congress enacted CAFA in order to “amend the proce-
dures that apply to consideration of interstate class ac-
tions.” 119 Stat. 4. In doing so, Congress recognized that
“[c]lass action lawsuits are an important and valuable part
of the legal system.” CAFA §2. It was concerned, however,
that certain requirements of federal diversity jurisdic-
tion, 

. §1332, had functioned to “kee[p] cases of
national importance” in state courts rather than federal
courts. CAFA §2.
   CAFA accordingly loosened the requirements for diver-
sity jurisdiction for two types of cases—“class actions” and
“mass actions.” The Act defines “class action” to mean
“any civil action filed under rule 23 of the Federal Rules of
Civil Procedure or similar State statute or rule of judicial
procedure.” 

. §1332(d)(1)(B). And it defines
“mass action” to mean “any civil action . . . in which mone-
tary relief claims of 100 or more persons are proposed
to be tried jointly on the ground that the plaintiffs’
claims involve common questions of law or fact.”
§1332(d)(11)(B)(i).
   For class and mass actions, CAFA expanded diversity
jurisdiction in two key ways. First, it replaced the ordi-
nary requirement of complete diversity of citizenship
among all plaintiffs and defendants, see State Farm Fire
& Casualty Co. v. Tashire, 

, 530–531 (1967),
with a requirement of minimal diversity. Under that re-
quirement, a federal court may exercise jurisdiction over a
class action if “any member of a class of plaintiffs is
a citizen of a State different from any defendant.”
§1332(d)(2)(A). The same rule applies to mass actions.
See §1332(d)(11)(A) (“[A] mass action shall be deemed . . .
removable under [§§1332(d)(2) through (d)(10)]”). Second,
whereas §1332(a) ordinarily requires each plaintiff’s claim
to exceed the sum or value of $75,000, see Exxon Mobil
                     Cite as: 571 U. S. ____ (2014)                    3

                          Opinion of the Court

Corp. v. Allapattah Services, Inc., 

, 554–555
(2005), CAFA grants federal jurisdiction over class and
mass actions in which the aggregate amount in contro-
versy exceeds $5 million. §§1332(d)(2), (d)(6), (d)(11)(A).
Class and mass actions filed in state court that satisfy
CAFA’s requirements may be removed to federal court, 

. §1453, but federal jurisdiction in a mass action,
unlike a class action, “shall exist only over those plaintiffs”
whose claims individually satisfy the $75,000 amount in
controversy requirement, §1332(d)(11)(B)(i).1
                              B
   Respondents manufacture liquid crystal displays, or
LCDs. In March 2011, the State of Mississippi sued them
in state court, alleging that they had formed an interna-
tional cartel to restrict competition and raise prices in
the LCD market. The State claimed that these actions vio-
lated two Mississippi statutes: the Mississippi Antitrust Act,
Miss. Code Ann. §75–21–1 et seq. (2009), and the Missis-
sippi Consumer Protection Act, §75–24–1 et seq. (2009 and
Cum. Supp. 2013). The State sought injunctive relief and
civil penalties under both statutes, along with punitive
damages, costs, and attorney’s fees. It also sought restitu-
tion for its own purchases “of LCD products and the pur-
chases of its citizens.” App. to Brief in Opposition 65a;
§75–24–11.
   Respondents filed a notice to remove the case from state
to federal court, arguing that the case was removable
under CAFA as either a “class action” or a “mass action.”
The District Court ruled that the suit did not qualify as
a “class action” because it was “not brought pursuant to
Federal Rule of Civil Procedure 23 or a ‘similar State
statute or rule of judicial procedure.’ ” 876 F. Supp. 2d
——————
  1 CAFA provides certain exceptions for class actions that involve mat-

ters of principally local or state concern. See 

. §§1332(d)(3)–
(5). None of them are at issue in this case.
4        MISSISSIPPI EX REL. HOOD v. AU OPTRONICS CORP.

                             Opinion of the Court

758, 769 (SD Miss. 2012). But it held that the suit did
qualify as a “mass action,” because “[i]t is a civil action ‘in
which monetary relief claims of 100 or more persons are
proposed to be tried jointly on the ground that the plain-
tiffs’ claims involve common questions of law or fact.’ ” 

The District Court reached that conclusion on the
basis of Fifth Circuit precedent in Louisiana ex rel. Cald-
well v. Allstate Ins. Co., 

(CA5 2008), which it
understood to “stan[d] for the proposition that the words
‘persons’ and ‘plaintiffs’ in [the mass action definition] are
to be defined as ‘real parties in interest.’ 

. Applying that rule, the court found that 100 or
more unidentified Mississippi consumers had purchased
LCD screens and were therefore real parties in interest to
the State’s restitution claim. 

the
“possibility that a ‘mass action’ should be thought of as a
‘mass joinder,’ ”—that is, as a suit involving 100 or more
“named plaintiffs.” Ibid., n. 9. But it deemed that inter-
pretation to be foreclosed by Caldwell.
   The District Court nonetheless remanded the case to
state court on the basis of CAFA’s “general public excep-
tion,” which excludes from the “mass action” definition
“any civil action in which . . . all of the claims in the action
are asserted on behalf of the general public (and not on
behalf of individual claimants or members of a purported
class) pursuant to a State statute specifically authorizing
such action.” 

. §1332(d)(11)(B)(ii)(III).
   The Court of Appeals reversed. 

(CA5
2012). It agreed with the District Court’s determination
that Mississippi’s suit is not a “class action” under CAFA.2

It also agreed that, under Caldwell, the suit
qualifies as a “mass action” because “[t]he real parties in
interest in Mississippi’s suit are those more than 100 . . .
individual citizens who purchased the [LCD] products
——————
    2 Respondents   do not challenge this ruling before this Court.
                     Cite as: 571 U. S. ____ (2014)                     5

                          Opinion of the Court

within 

. It disagreed, how-
ever, with the District Court’s ruling that the suit falls
within the general public exception. 

Judge Elrod concurred in the judgment, noting that after
the Fifth Circuit’s decision in Caldwell, three Courts of
Appeals had deemed similar lawsuits not to be mass ac-
tions removable under CAFA.4 We granted certiorari to
resolve this split of authority, 569 U. S. ___ (2013), and
now reverse.
                              II

                              A

  Our analysis begins with the statutory text. Sebelius v.
Cloer, 569 U. S. ___, ___ (2013) (slip op., at 6). The statute
provides:
     “[T]he term mass action means any civil action (except
     a [class action]) in which monetary relief claims of 100
     or more persons are proposed to be tried jointly on
     the ground that the plaintiffs’ claims involve common
     questions of law or fact, except that jurisdiction shall
     exist only over those plaintiffs whose claims in a mass
     action satisfy the jurisdictional amount requirements
     under subsection (a).” §1332(d)(11)(B)(i).
  The parties do not dispute that this provision encom-
passes suits that are brought jointly by 100 or more
named plaintiffs who propose to try their claims together.
The question is whether the provision also includes suits
——————
   3 The Court of Appeals did so on the rationale that because individual

Mississippi consumers are real parties in interest to the State’s restitu-
tion claim, the general public exception’s requirement that “all of
the claims” must be “asserted on behalf of the general public (and not
on behalf of individual claimants)” was not satisfied. 

.
§1332(d)(11)(B)(ii)(III).
   4 See AU Optronics Corp. v. South Carolina, 

(CA4

2012); Nevada v. Bank of Am. Corp., 

(CA9 2012); LG
Display Co. v. Madigan, 

(CA7 2011).
6     MISSISSIPPI EX REL. HOOD v. AU OPTRONICS CORP.

                      Opinion of the Court

brought by fewer than 100 named plaintiffs on the theory
that there may be 100 or more unnamed persons who are
real parties in interest as beneficiaries to any of the plain-
tiffs’ claims. Respondents argue that the provision covers
such suits because “claims of 100 or more persons” refers
to “the persons to whom the claim belongs, i.e., the real
parties in interest to the claims,” regardless of whether
those persons are named or unnamed. Brief for Respond-
ents 19 (emphasis in original). We disagree.
   To start, the statute says “100 or more persons,” not
“100 or more named or unnamed real parties in interest.”
Had Congress intended the latter, it easily could have
drafted language to that effect. Indeed, when Congress
wanted a numerosity requirement in CAFA to be satisfied
by counting unnamed parties in interest in addition to
named plaintiffs, it explicitly said so: CAFA provides that
in order for a class action to be removable, “the number
of members of all proposed plaintiff classes” must be 100
or greater, §1332(d)(5)(B), and it defines “class members”
to mean “the persons (named or unnamed) who fall within
the definition of the proposed or certified class,”
§1332(d)(1)(D). Congress chose not to use the phrase
“named or unnamed” in CAFA’s mass action provision, a
decision we understand to be intentional. See Dean v.
United States, 

, 573 (2009) (“ ‘[W]here Con-
gress includes particular language in one section of a
statute but omits it in another section of the same Act, it
is generally presumed that Congress acts intentionally
and purposely in the disparate inclusion or exclusion’ ”).
   More fundamentally, respondents’ interpretation cannot
be reconciled with the fact that the “100 or more persons”
referred to in the statute are not unspecified individuals
who have no actual participation in the suit, but instead
the very “plaintiffs” referred to later in the sentence—the
parties who are proposing to join their claims in a single
trial. Congress made this understanding evident in two
                  Cite as: 571 U. S. ____ (2014)            7

                      Opinion of the Court

key ways.
   First, we presume that “ ‘Congress is aware of existing
law when it passes legislation.’ ” Hall v. United States,
566 U. S. ___, ___ (2012) (slip op., at 9). Here, Congress
used the terms “persons” and “plaintiffs” just as they are
used in Federal Rule of Civil Procedure 20, governing
party joinder. Where §1332(d)(11)(B)(i) requires that the
“claims of 100 or more persons [must be] proposed to be
tried jointly on the ground that the plaintiffs’ claims in-
volve common questions of law or fact,” Rule 20 provides
that “[p]ersons may join in one action as plaintiffs if they
assert any right to relief jointly . . . and any question of
law or fact common to all plaintiffs will arise in the ac-
tion.” Thus, just as it is used in Rule 20, the term “per-
sons” in §1332(d)(11)(B)(i) refers to the individuals who
are proposing to join as plaintiffs in a single action.
   Second, respondents’ interpretation of “persons” cannot
square with the statute’s requirement that the claims of
the “100 or more persons” must be proposed for joint trial
“on the ground that the plaintiffs’ claims involve common
questions of law or fact.” §1332(d)(11)(B)(i). It is difficult
to imagine how the claims of one set of unnamed individ-
uals could be proposed for joint trial on the ground that the
claims of some completely different group of named plain-
tiffs share common questions. The better understanding
is that Congress meant for the “100 or more persons” and
the proposed “plaintiffs” to be one and the same.
   Recognizing that the statute’s use of the term “persons”
could be a reference to proposed plaintiffs, respondents
assert that “plaintiffs,” like “persons,” should be construed
to “includ[e] both named and unnamed real parties in in-
terest.” Brief for Respondents 24. But that stretches
the meaning of “plaintiff” beyond recognition. The term
“plaintiff” is among the most commonly understood of
legal terms of art: It means a “party who brings a civil suit
in a court of law.” Black’s Law Dictionary 1267 (9th ed.
8      MISSISSIPPI EX REL. HOOD v. AU OPTRONICS CORP.

                          Opinion of the Court

2009); see also Webster’s Third New International Dic-
tionary 1729 (1961) (defining “plaintiff” to mean “one who
commences a personal action or lawsuit,” or “the complain-
ing party in any litigation”). It certainly does not mean
“anyone, named or unnamed, whom a suit may benefit,” as
respondents suggest.5
   Moreover, Congress used the term “plaintiffs” twice in
the mass action provision. The provision encompasses
actions in which monetary “claims of 100 or more persons
are proposed to be tried jointly on the ground that the
plaintiffs’ claims involve common questions,” and it then
provides that “jurisdiction shall exist only over those
plaintiffs whose claims in a mass action satisfy the juris-
dictional amount requiremen[t]” of $75,000.          §1332(d)
(11)(B)(i). If respondents are correct that “plaintiffs”
means unnamed parties in interest where it is used the
first time, then so too the second. After all, the “pre-
sumption that a given term is used to mean the same
thing throughout a statute” is “at its most vigorous when a
term is repeated within a given sentence.” Brown v.
Gardner, 

, 118 (1994).
   Yet if the term “plaintiffs” is stretched to include all
unnamed individuals with an interest in the suit, then
§1332(d)(11)(B)(i)’s requirement that “jurisdiction shall
exist only over those plaintiffs whose claims [exceed
$75,000]” becomes an administrative nightmare that
Congress could not possibly have intended, see Griffin v.
Oceanic Contractors, Inc., 

, 575 (1982). How
is a district court to identify the unnamed parties whose
claims in a given case are for less than $75,000? Would
the court in this case, for instance, have to hold an eviden-
tiary hearing to determine the identity of each of the
——————
  5 Congress could of course require a real party in interest inquiry in a

statute that uses the term “plaintiff” simply by saying so. But it has
not done that here.
                    Cite as: 571 U. S. ____ (2014)                   9

                         Opinion of the Court

hundreds of thousands of unnamed Mississippi citizens
who purchased one of respondents’ LCD products between
1996 and 2006 (the period alleged in the complaint)? Even
if it could identify every such person, how would it ascer-
tain the amount in controversy for each individual claim?
Respondents suggest that “[i]n some circumstances, de-
fendants may be able to identify from their payment rec-
ords any persons who may have claims for overpayments,”
but they stop notably short of claiming to possess such
decades-old records themselves. Brief for Respondents 25.
   Furthermore, what would happen with individuals
whose claims were valued at less than $75,000? The
District Court in this case suggested that if the suit were
deemed a mass action, it would sever the claim for “resti-
tution for losses incurred by individuals claiming less than
or equal to $75,000 each” and remand that claim back to
state court, while allowing the other claims (including the
restitution claims exceeding $75,000) to proceed in federal

. Even respondents do not
defend that outcome, presumably because it would mean
that much of the State’s lawsuit could proceed in state
court after all, simultaneously with the newly severed
parallel federal action.6
   We think it unlikely that Congress intended that federal
district courts engage in these unwieldy inquiries. By
contrast, interpreting “plaintiffs” in accordance with its
usual meaning—to refer to the actual named parties who
——————
  6 Respondents suggest that a district court might be able to exercise

supplemental jurisdiction over the claims that fall beneath $75,000,
thereby avoiding the problem of identifying and remanding such claims
to the state court. We need not decide the issue here, but we note that
at least one Court of Appeals has rejected that view. See Lowery v.
Alabama Power Co., 

, 1206, n. 51 (CA11 2007) (holding
that because supplemental jurisdiction does not apply where a federal
statute “ ‘expressly provide[s] otherwise,’ ” 

. §1367(a), the
mass action provision’s explicit exclusion of jurisdiction over claims
beneath $75,000 negates supplemental jurisdiction over such claims).
10    MISSISSIPPI EX REL. HOOD v. AU OPTRONICS CORP.

                     Opinion of the Court

bring an action—leads to a straightforward, easy to ad-
minister rule under which a court would examine whether
the plaintiffs have pleaded in good faith the requisite
amount. See Horton v. Liberty Mut. Ins. Co., 

, 353 (1961). Our decision thus comports with the
commonsense observation that “when judges must decide
jurisdictional matters, simplicity is a virtue.” See Stand-
ard Fire Ins. Co. v. Knowles, 568 U. S. ___, ___ (2013) (slip
op., at 6).
                               B
   Our reading of the mass action provision’s text is rein-
forced by the statutory context. See Mohamad v. Palestin-
ian Authority, 566 U. S. ___, ___ (2012) (slip op., at 5–6).
   First, the provision of CAFA governing transfer motions
confirms our view that the term “plaintiffs” refers to actual
named parties as opposed to unnamed real parties in
interest. That provision, §1332(d)(11)(C)(i), provides that
once a mass action has been removed to federal court, it
“shall not thereafter be transferred to any other court . . .
unless a majority of the plaintiffs in the action request
transfer.” If respondents are correct that “plaintiffs”
means “unnamed parties in interest,” it will be surpass-
ingly difficult for a court to decide in a case like this one
whether an action may be transferred. The District Court
itself acknowledged this problem, noting that it would
have to identify and communicate with “hundreds of thou-
sands if not millions of real parties in interest” to “pol[l]
[them] about their preferred forum” if respondents’ inter-
pretation were 

.
   The context in which the mass action provision was
enacted lends further support to our conclusion. Congress’
overriding concern in enacting CAFA was with class ac-
tions. See Preamble, 119 Stat. 4 (describing CAFA as an
“[a]ct to amend the procedures that apply to consideration
of interstate class actions”); CAFA §2 (Congress’ findings
                    Cite as: 571 U. S. ____ (2014)                  11

                         Opinion of the Court

with respect to class actions). The mass action provision
thus functions largely as a backstop to ensure that CAFA’s
relaxed jurisdictional rules for class actions cannot be
evaded by a suit that names a host of plaintiffs rather
than using the class device. Respondents’ argument fails
to recognize this key distinction. Their position is ulti-
mately that “[t]his action is similar to a class action,” such
that it should be removed. Brief for Respondents 27. But
if Congress had wanted representative actions brought by
States as sole plaintiffs to be removable under CAFA on
the theory that they are in substance no different from
class actions, it would have done so through the class
action provision, not the one governing mass actions.7
                             III
   Rather than relying on the text of CAFA as the source of
its real party in interest inquiry, the Court of Appeals
appeared to find such an inquiry necessary on the basis of
what it understood to be a background principle: that
“federal courts look to the substance of the action and not
only at the labels that the parties may attach.” 

. This was error.
   We have interpreted the diversity jurisdiction statute to
require courts in certain contexts to look behind the plead-
ings to ensure that parties are not improperly creating or
destroying diversity jurisdiction. We have held, for exam-
ple, that a plaintiff may not keep a case out of federal
court by fraudulently naming a nondiverse defendant.
Wecker v. National Enameling & Stamping Co., 

, 185–186 (1907). Nor may a plaintiff create diversity
by collusively assigning his interest in an action. Kramer
v. Caribbean Mills, Inc., 

, 825–830 (1969);
——————
  7 The  parties both point to the “general public exception,”
§1332(d)(11)(B)(ii)(III), in support of their respective positions. But
because the foregoing arguments resolve this case, we need not con-
strue that provision here.
12    MISSISSIPPI EX REL. HOOD v. AU OPTRONICS CORP.

                     Opinion of the Court

see also 

. §1359. And in cases involving a State
or state official, we have inquired into the real party in
interest because a State’s presence as a party will destroy
complete diversity. Missouri, K. & T. R. Co. v. Missouri
Railroad and Warehouse Comm’rs, 

, 58–59
(1901).
  But the question in this case is not simply whether
there exists some background principle of analyzing the
real parties in interest to a suit; the question is whether
Congress intended that courts engage in that analysis
when deciding whether a suit is a mass action. Recogniz-
ing this fact, respondents do not argue that the real party
in interest inquiry employed in the above cases somehow
supersedes the text of CAFA; they instead argue that we
should read CAFA in light of those cases because “ ‘Con-
gress expects its statutes to be read in conformity with
this Court’s precedents.’ ” Brief for Respondents 19 (quot-
ing United States v. Wells, 

, 495 (1997)). For
two reasons, however, we conclude that Congress did not
intend the background inquiry to apply to the mass action
provision.
  First, it makes sense to infer Congress’ intent to incor-
porate a background principle into a new statute where
the principle has previously been applied in a similar
manner. But that is not the case here. The background
real party in interest inquiry identifies what party’s (or
parties’) citizenship should be considered in determining
diversity. The inquiry that respondents urge is quite dif-
ferent: It is an attempt to count up additional unnamed
parties in order to satisfy the mass action provision’s
numerosity requirement. Respondents offer no reason to
believe that Congress intended to extend the real party
inquiry to this new circumstance, and so any presumption
that Congress wanted to incorporate the inquiry, if it
exists in this case at all, would be comparatively weak. Cf.
Meyer v. Holley, 

, 286 (2003) (“Congress’
                    Cite as: 571 U. S. ____ (2014)                13

                        Opinion of the Court

silence, while permitting an inference that Congress in-
tended to apply ordinary background tort principles,
cannot show that it intended to apply an unusual modifi-
cation of those rules”).8
   Second, even if the background principle had previously
been applied in the manner sought by respondents, Con-
gress provided express indications that it did not want the
principle to apply to the mass action provision. It speci-
fied that “the term ‘mass action’ shall not include any civil
action in which . . . the claims are joined upon motion of a
defendant.” §1332(d)(11)(B)(ii)(II). By prohibiting de-
fendants from joining unnamed individuals to a lawsuit in
order to turn it into a mass action, Congress demonstrated
its focus on the persons who are actually proposing to join
together as named plaintiffs in the suit. Requiring district
courts to pierce the pleadings to identify unnamed persons
interested in the suit would run afoul of that intent.
Moreover, as already discussed, Congress repeatedly used
the word “plaintiffs” to describe the 100 or more persons
whose claims must be proposed for a joint trial. That word
refers to actual, named parties—a concept inherently at
odds with the background inquiry into unnamed real
parties in interest, who by definition are never plaintiffs.
Congress thus clearly displaced a background real party in
interest inquiry, even assuming one might otherwise
apply. Cf. Barnhart v. Sigmon Coal Co., 

,
459, n. 16 (2002).

——————
  8 We have also applied a real party in interest inquiry in contexts

other than that of determining citizenship for purposes of diversity
jurisdiction. See North Dakota v. Minnesota, 

, 374–376
(1923) (state sovereign immunity); Oklahoma ex rel. Johnson v. Cook,

, 392–393 (1938) (original jurisdiction). But even if we
were to indulge in a presumption that Congress somehow intended to
import the inquiry applied in those particular contexts into the mass
action provision’s distinct numerosity requirement, we would find any
such presumption overridden by CAFA’s text.
14    MISSISSIPPI EX REL. HOOD v. AU OPTRONICS CORP.

                     Opinion of the Court

                        *   *    *
  For the foregoing reasons, the judgment of the United
States Court of Appeals for the Fifth Circuit is reversed,
and the case is remanded for further proceedings con-
sistent with this opinion.
                                          It is so ordered.