                FOR PUBLICATION

  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT


APRIL BAIN; BHAVINI BHAKTA;              No. 16-55768
CLARE SOBETSKI,
              Plaintiffs-Appellants,       D.C. No.
                                        2:15-cv-02465-
                 v.                       SVW-AJW

CALIFORNIA TEACHERS
ASSOCIATION; NATIONAL                      OPINION
EDUCATION ASSOCIATION;
CALIFORNIA FEDERATION OF
TEACHERS; AMERICAN FEDERATION
OF TEACHERS; UNITED TEACHERS
LOS ANGELES; UNITED TEACHERS OF
RICHMOND CTA/NEA; RAMON
CORTINES, in his capacity as
Superintendent of Los Angeles
Unified School District; BRUCE
HARTER, in his capacity as
Superintendent of West Contra Costa
Unified School District; DAVID
VANNASDALL, in his capacity as
Superintendent of Arcadia Unified
School District,
               Defendants-Appellees.



      Appeal from the United States District Court
          for the Central District of California
      Stephen V. Wilson, District Judge, Presiding
2                BAIN V. CALIF. TEACHERS ASS’N

            Argued and Submitted December 6, 2017
                     Pasadena, California

                        Filed June 11, 2018

        Before: Paul J. Kelly, Jr., * Consuelo M. Callahan,
                and Carlos T. Bea, Circuit Judges.

                   Opinion by Judge Callahan


                          SUMMARY **


                            Civil Rights

    The panel dismissed as moot an appeal by public school
teacher plaintiffs from the district court’s dismissal of their
action alleging that their Unions’ requirement that they pay
a fee to support the Unions’ political and ideological
activities violated their constitutional right to free speech.

    The panel determined that a change in plaintiffs’
professional circumstances during the pendency of this
appeal fundamentally altered the posture of this case.
Because plaintiffs had disassociated from their respective
Unions, they could no longer benefit from the injunctive and
declaratory relief they sought, and therefore their appeal was
moot. The panel rejected plaintiffs’ attempt to transform

    *
      The Honorable Paul J. Kelly, Jr., United States Circuit Judge for
the U.S. Court of Appeals for the Tenth Circuit, sitting by designation.
    **
       This summary constitutes no part of the opinion of the court. It
has been prepared by court staff for the convenience of the reader.
              BAIN V. CALIF. TEACHERS ASS’N                  3

their lawsuit from a request for prospective equitable relief
into a plea for money damages. The panel noted that
plaintiffs had consistently represented throughout the
litigation that they were seeking only declaratory and
injunctive relief.

    The panel further denied plaintiffs’ motion to add an
organizational plaintiff, the Association of American
Educators, to their suit under Federal Rule of Civil
Procedure 21. The panel held that Rule 21 may not be used
to rehabilitate a court’s jurisdiction where a case becomes
moot on appeal. The panel further held that even if mootness
were not an insurmountable barrier to considering a Rule 21
motion, the panel would still deny the motion because
Association failed to satisfy the criteria for Rule 21 joinder.
The panel dismissed plaintiffs’ appeal and remanded to the
district court with instructions to dismiss the case without
vacating its judgment.


                         COUNSEL

Joshua S. Lipshutz (argued), Gibson Dunn & Crutcher LLP,
San Francisco, California; Theodore J. Boutrous Jr.,
Marcellus McRae, and Samuel Eckman, Gibson Dunn &
Crutcher LLP, Los Angeles, California; Kyle Hawkins,
Gibson Dunn & Crutcher LLP, Dallas, Texas; Michael R.
Huston, Gibson Dunn & Crutcher LLP, Washington, D.C.;
for Plaintiffs-Appellants.

Eric A. Harrington (argued), Jason Walta, and Alice
O’Brien, National Education Association, Washington,
D.C., for Defendants-Appellees.
4             BAIN V. CALIF. TEACHERS ASS’N

                         OPINION

CALLAHAN, Circuit Judge:

    Plaintiffs-Appellants are public school teachers in
California who were, at the time they filed their lawsuit,
members of the Defendants-Appellees public sector
teachers’ Unions. Plaintiffs claim that their Unions’
requirement that they pay a fee to support the Unions’
political and ideological activities violates their
constitutional right to free speech. While “[public sector]
union[s] remain[] as free as any other entity to participate in
the electoral process with all available funds other than []
state-coerced agency fees lacking affirmative permission,”
Davenport v. Washington Educ. Ass’n, 551 U.S. 177, 190
(2007), Plaintiffs reason that, as exclusive bargaining
representatives under California law, the Unions are state
actors and thus subject to the First Amendment’s
proscriptions. And because the First Amendment prohibits
state actors from infringing individuals’ right to free speech,
Plaintiffs argue that their Unions’ requirement that Union
members pay a political fee violates their and other
members’ constitutional rights.

     A change in Plaintiffs’ professional circumstances
during the pendency of this appeal fundamentally alters the
posture of this case. Plaintiffs have disassociated from their
respective Unions, meaning they can no longer benefit from
the injunctive and declaratory relief they seek. Their appeal
is therefore moot. Perhaps cognizant of the consequences of
their actions, Plaintiffs have filed a motion to add the
Association of American Educators (“AAE”) to their suit as
an organizational Plaintiff under Federal Rule of Civil
Procedure 21. But because we hold that Rule 21 is an
improper vehicle to resuscitate a moot case, we deny the
motion and dismiss Plaintiffs’ appeal as moot.
                BAIN V. CALIF. TEACHERS ASS’N                        5

                                  I.

     California law accommodates agency shop 1
arrangements between public sector teachers’ unions and
public school employers. Cal. Gov’t Code §§ 3343.1; 3544–
3544.9. To establish a union, public school teachers must
first form a bargaining unit. Id. § 3344. If a majority of
teachers in the unit elect to negotiate collectively with their
employer, then the union “may become the exclusive
representative for the employees of [that] unit for purposes
of meeting and negotiating.” Id. § 3544(a), (b). Once a
union gains status as the exclusive bargaining representative,
the public employer may bargain with only that union. Id.
§ 3543.1(a).

    Like many States, California allows public sector unions
to charge a “fair share service fee”—commonly known as an
“agency fee”—to those public employees who do not join
the exclusive bargaining representative. Id. §§ 3543(a),
3546. Nonmembers pay less than their union-member
counterparts because California law permits a union to
charge nonmembers only “chargeable fees”—i.e., fees
related to a union’s collective bargaining activities. 2 Id.
§ 3546(a). Union members, by contrast, are subject to the
internal rules of the union, which, as is pertinent here,

    1
      An “agency shop” differs from a “union shop”—a term used in
some of the cases cited in this opinion—in that the former refers to
unions in which membership is voluntary, whereas a “union shop”
arrangement means that all employees are technically union members.
Kidwell v. Transp. Commc’ns Int’l Union, 946 F.2d 283, 291 (4th Cir.
1991).
    2
      The schools automatically deduct these “chargeable fees” from all
teachers’ paychecks. Cal. Gov’t Code § 3543.1(d); see Cal. Educ. Code
§§ 45060, 45061, 45061.5, 45168.
6               BAIN V. CALIF. TEACHERS ASS’N

include paying “non-chargeable fees”—e.g., fees that fund
members-only benefits and the union’s political, ideological,
and other activities unrelated to collective bargaining. See
id. § 3543.1(d). Supreme Court precedent and California
law prohibit unions from charging objecting nonmembers
for the unions’ First Amendment-protected expressive
political activities. Abood v. Detroit Bd. of Ed., 431 U.S.
209, 234–36 (1977); Cumero v. Pub. Emp’t Relations Bd.,
49 Cal. 3d 575, 594 (1989).

    Consistent with their own internal policies, the Unions in
the instant matter provide certain members-only benefits.
For example, Union members enjoy the privilege of voting
on collective bargaining agreements (“CBA”) and sitting on
school district committees. In addition, the Unions provide
employment-related benefits such as disability insurance,
free legal representation, life insurance, death and
dismemberment benefits, and disaster relief. Nonmembers
are not entitled to these benefits, nor are they charged for
them. Cumero, 49 Cal. 3d at 587–88 (under California law,
nonmembers “should not be required to support activities
which are beyond the Association’s representational
obligations” (emphasis in original)). And while the Unions
could negotiate for state-offered insurance benefits in the
collective bargaining process—e.g., California’s State
Disability Insurance and Paid Family Leave (“SDI”)
program—they have opted not to do so and instead offer
alternative insurance to their members. 3



    3
      If the Unions did negotiate for SDI, then such insurance would be
provided to all teachers—members and nonmembers alike. By the same
token, all teachers would be required to pay insurance premiums on the
policies. Cal. Unemp. Ins. Code § 710.4.
                 BAIN V. CALIF. TEACHERS ASS’N                            7

    Plaintiffs April Bain, Clare Sobetski, and Bhavini
Bhakta were public school teachers in California who
elected to join the Unions. They are no longer Union
members, however, because they have left their teaching
positions. Bain’s Union membership ended in June 2017
and Sobetski’s ended in August 2017. For her part, Bhakta’s
Union membership ended in August 2016 when she was
promoted to Assistant Principal at Arcadia High School, a
position that makes her ineligible for Union membership.

                                    II.

     Plaintiffs filed their operative Second Amended
Complaint (“SAC”) in October 2015 in the Central District
of California as a 42 U.S.C. § 1983 civil rights action. Both
in the district court and on appeal, Plaintiffs claim violations
of their right to free speech under the First Amendment and
Article I, § 2(a) of the California Constitution.4 Plaintiffs
argue that the Unions and state School Boards work together
to force teachers to either finance the Unions’ political
activities and thereby surrender their free speech rights, or
forgo the benefits of union membership and keep their
constitutional rights intact. Plaintiffs assert that because
membership benefits are so enticing, most teachers will
acquiesce, join the Unions, and pay the non-chargeable—
i.e., political—fee.


    4
       The First Amendment to the U.S. Constitution provides that
“Congress shall make no law . . . abridging the freedom of speech, or of
the press; or the right of the people peaceably to assemble, and to petition
the Government for a redress of grievances.” Article I, § 2(a) of the
California Constitution provides that “[e]very person may freely speak,
write and publish his or her sentiments on all subjects, being responsible
for the abuse of this right. A law may not restrain or abridge liberty of
speech or press.”
8             BAIN V. CALIF. TEACHERS ASS’N

    Plaintiffs seek declaratory relief in the form of (1) a
declaration that California’s agency shop laws, collective
bargaining laws, and the CBAs entered into the by the
Unions violate their constitutional rights; (2) a declaration
that those laws and CBAs coerce teachers into funding the
Unions’ political activities in violation of their constitutional
rights; and (3) a declaration that those laws and CBAs violate
Plaintiffs’ constitutional rights by forcing school
superintendents to deduct from teachers’ paychecks dues
that support the Unions’ non-chargeable activities. Plaintiffs
also seek an injunction (1) barring the Unions from denying
Union membership or any of its privileges based on a
teacher’s refusal to pay the non-chargeable fee; and
(2) barring school superintendents from deducting the non-
chargeable fee from Union members’ paychecks. Finally,
Plaintiffs seek “such additional or different relief as [the
district court] deems just and proper, including an award of
reasonable attorneys’ fees and the costs of this action.”

    The Unions filed a motion to dismiss the SAC under
Federal Rule of Civil Procedure 12(b)(6), which the district
court granted with prejudice. The court rejected Plaintiffs’
argument that the Unions’ internal membership rules
requiring their members to pay the non-chargeable fee
constitute state action. The court found unpersuasive
Plaintiffs’ theory that “the choice [teachers] face between the
benefits of union membership and the lack of benefits of
nonmember status ‘is a product of state action because the
coercion that California teachers experience could not exist
without the State.’” To the contrary, the court found that
because the Unions could decide, without any intervention
by the State, not to require their members to pay non-
chargeable fees, Plaintiffs challenged only a private decision
by the Unions.
              BAIN V. CALIF. TEACHERS ASS’N                   9

    The district court also rejected Plaintiffs’ argument that
the CBAs negotiated by the State and the Unions are infused
with state action through state legislation authorizing agency
shops. The court noted that the “agency shop arrangement
established by the State does not compel employees to
finance union activities unrelated to collective bargaining
unless they choose to join a union.” (emphasis added).
Citing the Fourth Circuit’s decision in Kidwell v.
Transportation Communications International Union,
946 F.2d 283 (4th Cir. 1991), the court reasoned that the
State’s recognition of the Unions as collective bargaining
representatives did not transform the Unions’ “internal
policies and practices” into state action. Accordingly,
because Plaintiffs failed to show that the Unions qua “state
actors” had infringed their constitutional rights, the district
court found no actionable claim for relief and dismissed the
case. Plaintiffs timely appealed.

                              III.

    We review a district court’s grant of a Rule 12(b)(6)
motion to dismiss for failure to state a claim de novo.
Edwards v. Marin Park, Inc., 356 F.3d 1058, 1061 (9th Cir.
2004). “A motion under Rule 12(b)(6) should be granted
only if ‘it appears beyond doubt that the plaintiff can prove
no set of facts in support of his claim which would entitle
him to relief,’ construing the complaint in the light most
favorable to the plaintiff.” Id. (internal citation omitted)
(quoting Conley v. Gibson, 355 U.S. 41, 45–46 (1957)). “To
survive a motion to dismiss, a complaint must contain
sufficient factual matter, accepted as true, to state a claim to
relief that is plausible on its face.” Ashcroft v. Iqbal,
556 U.S. 662, 678 (2009) (internal quotation marks
omitted). “Threadbare recitals of the elements of a cause of
10            BAIN V. CALIF. TEACHERS ASS’N

action, supported by mere conclusory statements, do not
suffice.” Id.

                             IV.

     We must first decide whether Plaintiffs’ appeal is moot
in light of their disassociation from the Unions. “[A]n actual
controversy must be extant at all stages of review, not merely
at the time the complaint is filed.” Arizonans for Official
English v. Arizona, 520 U.S. 43, 67 (1997) (internal
quotation marks and citation omitted). Thus, a plaintiff must
satisfy the irreducible constitutional minimum of Article III
standing at each stage of the litigation, including on appeal.
Standing requires a showing that a plaintiff has suffered an
(1) injury-in-fact that is actual or imminent and concrete and
particularized, rather than speculative or hypothetical;
(2) which is fairly traceable to the conduct complained of;
and (3) which is likely to be redressed by a favorable ruling.
Lujan v. Defenders of Wildlife, 504 U.S. 555, 560–61 (1992).

    Plaintiffs argue that a live controversy persists despite
the termination of their memberships in the Unions. First,
Plaintiffs rely on a catch-all claim for relief in their SAC,
which seeks “such additional or different relief as [the
district court] deems just and proper.” Second, Plaintiffs
argue that the district court could “issue restitution or other
equitable relief on its own.” Third, Plaintiffs reason that
because Bhakta still lives in California and works for one of
the school districts represented by a Union, she has standing
because it is conceivable she could rejoin the Union in the
future. None of these arguments are persuasive.

                              A.

    Plaintiffs’ first two arguments merge into one: that the
district court’s ability to grant restitution for past alleged
              BAIN V. CALIF. TEACHERS ASS’N                  11

constitutional violations under the umbrella of “such
additional or different relief” suffices to maintain a live
controversy. But, as the Unions point out, bootstrapping
restitution into an ancillary prayer for relief at this stage of
the litigation runs afoul of binding Ninth Circuit law.

    Until now, Plaintiffs never sought any type of money
damages. Injunctive relief—a requirement that the Unions
allow their members to abstain from paying a non-
chargeable political fee, or allow nonmembers to enjoy the
perquisites of Union membership—and a declaration that the
Unions’ operations are unconstitutional, form the body,
heart, and soul of Plaintiffs’ action. None of Plaintiffs’ three
complaints nor their briefing on appeal indicate any desire
for monetary relief. Moreover, restitution would not
vindicate all Union members’ First Amendment rights, even
though that is precisely what Plaintiffs seek to do. Instead,
at the eleventh hour, Plaintiffs propose to transform their
lawsuit from a request for prospective equitable relief into a
plea for money damages to remedy past wrongs.

    We have previously rejected such late-in-the-day
transformations. In Seven Words LLC v. Network Solutions,
260 F.3d 1089, 1092, 1095 (9th Cir. 2001), plaintiffs sought
injunctive and declaratory relief against a government
agency that refused to register their internet domain name,
which contained explicit words. By the time their case was
heard on appeal, the relevant words had already been given
to others to use as their own domain names and the defendant
had abandoned its policy of rejecting explicit words. Id. at
1095. In an attempt to save their appeal from mootness,
plaintiffs argued that they were still entitled to money
damages for past harms. Id.

    We rejected plaintiffs’ argument, concluding that
“[s]uch a late-in-the-day damages claim is inconsistent with
12            BAIN V. CALIF. TEACHERS ASS’N

our longstanding rule that we do not consider arguments not
raised in the briefs.” Id. at 1097. We explained that

       [o]ver and over again, throughout the various
       legal maneuvers, Seven Words consistently
       represented that it was seeking only
       declaratory and injunctive relief.            For
       example, not only did Seven Words, in its
       Seven Words II complaint, seek only “a
       declaration of its rights” and “injunctive
       relief,” but it similarly represented that it was
       “seeking declaratory relief” in its August
       1999 opposition to NSI’s motion to dismiss
       . . . . Seven Words did not . . . claim it was
       seeking damages . . . . The first time Seven
       Words raised damages in an effort to defeat
       mootness was in supplemental briefing on
       appeal.

Id. at 1096–97; see also Arizonans for Official English,
520 U.S. at 71 (a claim “extracted late in the day from [a]
general prayer for relief and asserted solely to avoid
otherwise certain mootness, b[ears] close inspection”); Fox
v. Bd. of Trustees of State Univ. of New York, 42 F.3d 135,
141 (2d Cir. 1994) (complaint’s prayer for “such other relief
as the Court deems just and proper” did not suffice to support
a late-in-the-day claim for nominal damages to avoid
mootness because “there is absolutely no specific mention in
the Complaint of nominal damages” (internal quotation
marks and adjustment omitted)); R.S. & V. Co. v. Atlas Van
Lines, 917 F.2d 348, 351 (7th Cir. 1990) (contract claim was
moot where complaint failed to seek nominal damages).

    Same here. Plaintiffs have, “over and over again,
throughout the various legal maneuvers . . . consistently
                 BAIN V. CALIF. TEACHERS ASS’N                            13

represented that [they were] seeking only declaratory and
injunctive relief.” Seven Words, 260 F.3d at 1096–97.
Indeed, as recently as their reply brief on appeal, Plaintiffs
summed up their requested relief as follows: “[The Unions’]
constitutional transgressions can be remedied by an order
operating upon the State directly . . . or by an order operating
upon Unions . . . .” 5 Neither option includes even a whiff of
a request for money damages.

    Plaintiffs cite Bayer v. Neiman Marcus Group, Inc.,
861 F.3d 853 (9th Cir. 2017), for the proposition that “[t]his
Court has implicitly concluded that claims for equitable
relief, such as restitution, are analyzed differently from
claims for nominal damages when considering mootness.”
Plaintiffs are correct that, in Bayer, we distinguished
equitable from legal relief, but that distinction had nothing
to do with that case’s separate mootness inquiry. 861 F.3d
at 868–69. In Bayer, we considered whether the plaintiff
could secure nominal damages where the statute at issue
provided for only equitable relief. Id. Our decision
addressed two issues: (1) whether nominal damages could

    5
         Plaintiffs’ position on appeal differs from their requested relief in
their SAC. Whereas the SAC seeks a declaration that California’s
agency shop statutes are unconstitutional, Plaintiffs on appeal seek to
enjoin the agency shop laws through “an order operating upon the State
. . . .” (emphasis added). But California is not a party to this action, and
failure to give California an opportunity to defend its own law before a
court strikes it down arguably runs afoul of the Federal Rules of Civil
Procedure and skirts a due process violation. See Fed. R. Civ. P. 65(d)(2)
(defining “[p]ersons [b]ound” by an order granting injunctive relief to
include “parties” or “other persons who are in active concert of
participation” with a party to the action); Hakeem v. Stinson, 39 F. App’x
674, 675 (2d Cir. 2002) (“Generally, we may order no injunctive relief
against non-parties . . . .”); cf. Catanzaro v. Michigan Dep’t of Corr., No.
08-11173, 2009 WL 2139210, at *1 (E.D. Mich. July 14, 2009) (“This
court has no authority to order relief for a non-party.”).
14            BAIN V. CALIF. TEACHERS ASS’N

be construed as equitable relief, and, if so, (2) whether the
plaintiff had put the defendant on sufficient notice that it
sought nominal damages in the district court. See id. at 869.
While Plaintiffs focus on the first issue, the second is the one
that applies here, and on that point, Bayer accords with Seven
Words.

     In Bayer, unlike here, the plaintiff “asserted a claim for
damages” in the district court in addition to stating a “general
prayer for such other relief as the district court deemed
proper.” Id. The plaintiff also “explicitly argued he was
entitled to nominal damages” before the district court. Id.
Thus, Bayer was “not a case in which the defendant lacked
notice that damages were sought until the plaintiff attempted
to wrest a claim for nominal damages from a general prayer
for relief for the first time on appeal.” Id. The exact opposite
is true here: Plaintiffs seek, for the first time on appeal, to
“wrest a claim for [restitution] from a general prayer for
relief” without prior notice to the Unions.

   Consistent with our decisions in Seven Words and Bayer,
we reject Plaintiffs’ attempt to manufacture jurisdiction and
avoid mootness by suddenly seeking restitution.

                              B.

    Plaintiffs argue that even if Bain and Sobetski no longer
have standing, Bhakta’s distinct situation salvages our
jurisdiction.     Although Bhakta canceled her union
membership when she was promoted, Plaintiffs note that,
unlike Bain and Sobetski, Bhakta has maintained her
employment—albeit as a non-unionized Assistant
Principal—with the school district where she was formerly
a unionized teacher. Plaintiffs contend that if Bhakta goes
back to teaching, “she would face the same coercion alleged
in the SAC.”
             BAIN V. CALIF. TEACHERS ASS’N                15

    The problem for Plaintiffs is that they fail to show any
intention by Bhakta to return to teaching. Standing requires
Bhakta to have an “actual or imminent” and “concrete and
particularized” injury. Defenders of Wildlife, 504 U.S. at
560. It cannot be merely “hypothetical” that she will teach
again. Id.; Summers v. Earth Island Institute, 555 U.S. 488,
493 (2009). The assertion that Bhakta could conceivably
return to her old job, without more, is precisely the type of
speculative “some day” intention the Supreme Court has
rejected as insufficient to confer standing. Defenders of
Wildlife, 504 U.S. at 564; see also Thomas v. Anchorage
Equal Rights Comm’n, 220 F.3d 1134, 1139 (9th Cir. 2000)
(en banc) (requiring a “concrete plan” rather than a
“hypothetical intent to violate the law” (internal quotation
marks omitted)).

    A case cited by Plaintiffs, Southern Oregon Barter Fair
v. Jackson County, Oregon, 372 F.3d 1128 (9th Cir. 2004),
actually makes the point. There, the plaintiff organization
had not held a major fair in years. Id. at 1134. But it had
made concrete efforts to hold another event, and because it
did so, it alleged a cognizable injury-in-fact. Id. Thus, the
case was not moot. Id. The court in Fair was quick to note,
however, that the case “would be moot if the [organization]
had entirely ceased to operate, left the business, and no
longer sought or intended to seek a license” to operate. Id.
(emphasis added). As Bayer similarly explained:

       A former employee currently seeking to be
       reinstated or rehired may have standing to
       seek injunctive relief against a former
       employer. But a former employee has no
       claim for injunctive relief addressing the
       employment practices of a former employer
       absent a reasonably certain basis for
16            BAIN V. CALIF. TEACHERS ASS’N

       concluding he or she has some personal need
       for prospective relief.

861 F.3d at 865 (emphasis added; internal citation omitted).

    Unlike in Fair, Plaintiffs do not allege that Bhakta
intends to return to teaching. And as in the Bayer
illustration, Plaintiffs have “produced no evidence to suggest
that [Bhakta] plans to [re-]seek employment” as a teacher in
the Arcadia Unified School District. Id. Accordingly,
Bhakta has not shown the requisite ongoing or imminent
injury-in-fact to preserve standing. The case is therefore
moot.

                             V.

    Our conclusion that Plaintiffs’ appeal is moot would be
the end of the matter but for their fourth-quarter motion to
add AAE as an organizational plaintiff under Federal Rule
of Civil Procedure 21. Rule 21 provides that “[o]n motion
or on its own, the court may at any time, on just terms, add
or drop a party. The court may also sever any claim against
a party.”

    Plaintiffs’ motion confronts several obstacles. Most
fundamentally, to grant Plaintiffs’ request we would first
need to hold that a court, having been deprived of
jurisdiction by way of mootness, may nevertheless resurrect
jurisdiction by adding a party to the suit. Second, we would
need to find that AAE has standing in its own right to pursue
Plaintiffs’ claims. And third, even if we ruled in favor of
Plaintiffs on these two jurisdictional issues, we would still
need to decide that Plaintiffs satisfy Rule 21’s criteria for
adding AAE to the suit.
                BAIN V. CALIF. TEACHERS ASS’N                        17

    Ultimately, despite its efforts, AAE fails to make the
grade because, we hold, Rule 21 is an improper vehicle for
reviving a moot case, and even if it were not, AAE does not
satisfy the requirements for Rule 21 joinder. 6

                                  A.

    By the time a case reaches the court of appeals, it has
undergone significant development. If it originated in
district court, a complaint has been served, an answer or
motion to dismiss has been filed, and discovery may have
been taken. All of this occurs in the context of a particular
dispute between particular parties.          Adding a party
midstream can alter the character of the litigation in material
ways, causing a plaintiff or defendant to adjust their theory
of the case, file additional or different motions, and modify
their legal strategy. Moreover, joining a party on appeal
carries an acute risk of prejudice because the opposing party
is deprived of the opportunity to develop the facts and law
as is relevant to the new party. For these reasons, Rule 21 is
“rarely” used on appeal. See Mullaney v. Anderson,
342 U.S. 415, 417 (1952).

    Of course, rarely is not never, and we have, in limited
circumstances, granted a Rule 21 motion to cure a
jurisdictional defect. But we have been careful to restrict
this exception to cases satisfying two narrow criteria: where
(1) failure to join a party would result in “meaningless
proceedings in the district court,” thereby thwarting the
interests of judicial economy, California Credit Union

    6
      We assume without deciding that AAE has organizational standing
to press Plaintiffs’ constitutional claims. See Hunt v. Wash. State Apple
Adver. Comm’n, 432 U.S. 333, 343 (1977) (setting forth the standard for
organizational standing).
18            BAIN V. CALIF. TEACHERS ASS’N

League v. City of Anaheim, 190 F.3d 997, 1001 (9th Cir.
1999), and where (2) joinder would allow the original
plaintiff to perfect jurisdiction for its claims and thereby
recover its requested relief, id. at 998; Mullaney, 342 U.S. at
416–17.

    Anaheim involved a suit brought by federal credit union
employees who contested an occupancy tax levied under the
City of Anaheim’s municipal code. 190 F.3d at 998. They
argued that the tax violated a federal statute granting credit
unions broad immunity from local taxation. Id. We granted
relief, but the Supreme Court vacated that decision, holding
that the Tax Injunction Act barred such suits unless the
United States was a party. Id. On remand, plaintiffs sought
to join the United States, and we granted the motion to solve
the jurisdictional problem that precluded plaintiffs from
securing their requested relief. Id. We explained that,

       [i]f we were to remand this case with
       instructions to dismiss or to have the United
       States litigate the merits of the tax exemption
       issue, the United States and the League, as
       co-plaintiffs, would simply rely on the
       League’s original complaint against
       Anaheim, submit the same materials that the
       League already filed in the district court, and
       receive a preordained judgment in their
       favor. The United States and the League
       “should not be compelled to jump through
       these judicial hoops merely for the sake of
       hypertechnical jurisdictional purity,” because
       judicial economy and considerations of
       practicalities outweigh any concern we have
       regarding jurisdictional purity.
              BAIN V. CALIF. TEACHERS ASS’N                19

Id. (emphasis added; internal citation omitted) (quoting
Newman-Green, Inc. v. Alfonzo-Larrain, 490 U.S. 826, 837
(1989)). We were quick to caution, however, that granting a
Rule 21 motion in such circumstances is “rare” and must be
“‘exercised sparingly.’” Id. at 999, 1001 (quoting Newman-
Green, 490 U.S. at 837); see also Mullaney, 342 U.S. at 417
(“Rule 21 will rarely come into play at [the appellate] stage
of a litigation.”).

    Mullaney involved a suit brought by a fishermen’s union
and its treasurer against the Alaska tax commissioner.
342 U.S. at 416–17. Once the case reached the Supreme
Court, the tax commissioner argued for the first time that
plaintiffs lacked standing absent joinder of members of the
union. Id. at 416. Petitioners then filed a motion to join two
of their members to cure any perceived jurisdictional defect,
and the Court granted the motion. Id. Critically, as in
Anaheim, joining the additional parties allowed the original
plaintiffs to recover. See id. at 416–17.

    Finally, Newman-Green involved a court of appeals’
decision to dismiss a dispensable non-diverse party to
perfect diversity jurisdiction. 490 U.S. at 836–37. There
was no question that a live controversy existed, or that the
court could still award relief to the original plaintiffs. See
id.

    The type of jurisdictional defect at issue in our case—
mootness—differs from those presented in Mullaney,
Anaheim, and Newman-Green. In those cases, a live
controversy existed between the original parties, but the
party joined or dropped was either necessary to the suit or,
in the case of Newman-Green, dispensable to the suit. The
original plaintiffs could recover so long as the additional
parties were added or dropped. By contrast, when a case
becomes moot the court can no longer award relief to the
20            BAIN V. CALIF. TEACHERS ASS’N

plaintiffs, and so the proper resolution is dismissal. Picrin-
Peron v. Rison, 930 F.2d 773, 775–76 (9th Cir. 1991); see
also North Carolina v. Rice, 404 U.S. 244, 246 (1971) (per
curiam) (“federal courts are without power to decide
questions that cannot affect the rights of litigants in the case
before them”). As we have previously observed, Rule 21 is
not designed to swap in new plaintiffs for the sake of
securing a judicial determination on the merits where the
original plaintiffs no longer have a stake in the outcome. See
Sable Commc’ns of California Inc. v. Pac. Tel. & Tel. Co.,
890 F.2d 184, 191 n.13 (9th Cir. 1989) (“Nothing on the face
of Rule 21 allows substitution of parties.”).

    The dangers of adding a party to “un-moot” a case are
substantial. First, unlike granting joinder to perfect
jurisdiction for the benefit of the original plaintiffs, joining
a party to replace the original plaintiffs effectively hatches a
new controversy on appeal, and without the benefit of
development in the district court. Second, allowing joinder
in such circumstances is contrary to the foundational
jurisdictional doctrines of mootness and standing, and
disserves the interests of judicial economy and judicial
restraint. As the Second Circuit has recognized, the
mootness doctrine would be rendered obsolete in many if not
most cases if Rule 21 could be used to revive a moot case.
Fox, 42 F.3d at 144 (discussing Fox v. Bd. of Trustees of the
State Univ. of New York, 148 F.R.D. 474, 482–89 (N.D.N.Y.
1993)). So long as a party could locate an eligible participant
with standing to pursue an action, a case could avoid ever
going moot. As the Northern District of New York held in
Fox, whose reasoning was incorporated by reference on
appeal:

       Rule 21 was also not enacted as a means for
       a party to avoid dismissal on mootness
              BAIN V. CALIF. TEACHERS ASS’N                  21

       grounds. If that were so, no case would ever
       become moot because a party who no longer
       had the requisite personal stake in the
       litigation, so as to satisfy the case or
       controversy requirement of Article III, would
       only have to move under Rule 21 for
       substitution of a party who could satisfy the
       requirement. That was not the purpose
       underlying the adoption of Rule 21.

Fox, 148 F.R.D. at 484, aff’d, 42 F.3d 135.

    We find the Second Circuit’s position compelled by the
Supreme Court’s decision in Board of School
Commissioners of City of Indianapolis v. Jacobs, 420 U.S.
128 (1975). There, six students sought a declaration that
certain regulations by the Indianapolis Board of School
Commissioners violated their First Amendment rights. Id.
at 128. The students’ complaint sought class certification for
all similarly situated high school students. Id. at 129. But
by the time the case reached the Supreme Court, the named
plaintiffs had graduated, rendering the appeal moot. Id. The
Court refused to replace the named plaintiffs with other
members of the putative class so that the appeal could
proceed because the class was never certified. Id. at 129–30.
The Court explained that “[t]he case is [] moot unless it was
duly certified as a class action pursuant to Fed. Rule Civ.
Proc. 23, a controversy still exists between petitioners and
the present members of the class, and the issue in
controversy is such that it is capable of repetition yet evading
review.” Id. at 129. While it appears no Rule 21 motion was
ever filed, the Court’s holding applies with particular force
to the instant matter. Jacobs stands for the proposition that
absent the unique circumstance of class certification, courts
lack the authority to replace a party with a new one once a
22            BAIN V. CALIF. TEACHERS ASS’N

case becomes moot. See id. at 129–30; Eckert v. Equitable
Life Assurance Soc’y of U.S., 227 F.R.D. 60, 63 (E.D.N.Y.
2005) (“[C]lass certification acts as a lifeboat for a claim that
would otherwise be moot . . . .”).

   Adding AAE on appeal also clashes with the Supreme
Court’s careful articulation of the Article III standing
doctrine.

        In limiting the judicial power to ‘Cases’ and
        ‘Controversies,’ Article III of the
        Constitution restricts it to the traditional role
        of Anglo-American courts, which is to
        redress or prevent actual or imminently
        threatened injury to persons caused by
        private or official violation of law. Except
        when necessary in the execution of that
        function, courts have no charter to review and
        revise legislative and executive action.

Summers, 555 U.S. at 492. Where the original plaintiffs no
longer have an actionable claim, replacing them with a new
plaintiff risks resolving a generalized grievance over
remedying an individualized injury. Lexmark Int’l, Inc. v.
Static Control Components, Inc., 134 S. Ct. 1377, 1386
(2014) (recognizing the prudential limitation on
“adjudication of generalized grievances” (internal quotation
marks omitted)). Such an approach not only strikes at
standing’s doctrinal underpinnings, but it is hardly
“necessary in the execution of” the court’s function to
“redress” an “injury”—after all, the plaintiffs that invoked
the court’s jurisdiction no longer have a redressable injury.

    The harm from courts arrogating power by giving short
shrift to the standing doctrine is particularly acute where, as
here, we are asked to pass on questions of constitutional
              BAIN V. CALIF. TEACHERS ASS’N                23

import. “If there is one doctrine more deeply rooted than
any other in the process of constitutional adjudication, it is
that we ought not to pass on questions of constitutionality
. . . unless such adjudication is unavoidable.” Clinton v.
Jones, 520 U.S. 681, 690, n.11 (1997) (internal quotation
marks omitted). It would turn this axiom on its head to hold
that we should “pass on questions of constitutionality” where
an appeal has become moot.

    For all these reasons, we join the Second Circuit in
holding that Rule 21 may not be used to rehabilitate a court’s
jurisdiction where a case becomes moot on appeal.
Accordingly, we deny Plaintiffs’ motion to join AAE as a
party to the instant action.

                             B.

    For the sake of completeness, we proceed to consider
whether AAE satisfies the criteria for Rule 21 joinder,
notwithstanding our holding that the appeal is moot. “[A]
party may join a lawsuit on appeal under Rule 21 when the
party seeking joinder [1] requests the same remedy as the
original party and [2] offers the same reasons for that remedy
and [3] earlier joinder would not have affected the course of
the litigation.” Anaheim, 190 F.3d at 999.

    AAE satisfies the first factor because both it and
Plaintiffs seek the same declaratory and injunctive relief.
While Plaintiffs also seek restitution in their post-merits
briefing, as explained in Part IV.A, supra, we do not credit
this eleventh-hour plea to convert a matter that was always
about securing prospective equitable relief into a claim for
money damages. However, AAE fails to carry its burden on
the second and third factors. AAE has not shown that it
seeks relief for the same reasons as the original Plaintiffs
24            BAIN V. CALIF. TEACHERS ASS’N

and, as a consequence, joining AAE presents a considerable
risk of prejudice to the Unions in their chosen defense.

    AAE’s interests and those of the Unions diverge in a
crucial way: AAE seeks to out-compete the Unions, whereas
Plaintiffs continue to support their Unions. Indeed, AAE
characterizes its mission as providing an “alternative to the
partisan politics . . . of the teacher labor unions.” AAE has
also “acknowledg[ed] that [its affiliates and affiliates of
public sector teachers’ unions] compete for membership
dues dollars, because as a practical matter both organizations
offer similar benefits . . . and one would not expect teachers
to pay two sets of dues for similar benefits.” Unified Sch.
Dist. No. 233 Johnson Cnty. v. Kansas Ass’n of Am.
Educators, 275 Kan. 313, 324 (2003) (internal quotation
marks omitted). In other words, join AAE, not the Unions.
Driving home the point, AAE recently stated that “[t]here is
a direct conflict between AAE’s mission” and collective
bargaining by the Unions, and that it “object[s] on policy
grounds to the positions taken by teachers’ unions in the
collective-bargaining process and outside of that process.”
Compl. at 11–12 (Yohn v. California Teachers Ass’n, No.
8:17-cv-00202-JLS-DFM (C.D. Cal. Feb. 6, 2017)).
Plaintiffs, by contrast, “value their unions,” in particular the
“support” their Unions provide in “negotiating with their
employers” through collective bargaining.

    The mis-match in objectives renders it implausible that
AAE seeks injunctive and declaratory relief to, as the
Plaintiffs desire, make Union membership more attractive to
teachers reluctant to pay the Unions’ non-chargeable fee. It
also means the Unions may have litigated the case
differently, and made alternative arguments, had AAE been
a party from the start. For example, the Unions likely would
have argued that AAE lacks organizational standing—a
              BAIN V. CALIF. TEACHERS ASS’N                 25

threshold question not implicated by the Plaintiffs’ original
action. The Unions may have also explored the distinction
between AAE’s members’ alleged First Amendment injury
and Plaintiffs’ own: Plaintiffs are Union members whose
free speech interests are allegedly infringed by the
requirement that they pay their Unions’ non-chargeable fee.
AAE, by contrast, does not allege that any of its members
are members of the Unions, let alone that they are subject to
the same fee.

    The legal import of this distinction is far from
speculative. The Supreme Court has consistently held that
unions—acting under the aegis of federal or state law—
infringe non-Union members’ free speech rights if they
compel nonmembers to finance the Unions’ political
activities—something AAE does not allege the Unions have
done here. See, e.g., Commc’ns Workers of Am. v. Beck,
487 U.S. 735, 758, 761 (1988) (“the [Railway Labor Act]
does not permit a union, over the objections of nonmembers,
to expend compelled agency fees on political causes”);
Abood, 431 U.S. at 234–36 (addressing the First Amendment
rights of nonmembers not to fund a union’s political and
ideological activities); cf. Ellis v. Railway Clerks, 466 U.S.
435, 455 n.14 (1984) (distinguishing “voluntary members”
from objecting “nonmembers”). Had AAE’s constitutional
claims been squarely presented in the district court and in the
merits briefing on appeal, the parties could have addressed
the applicability of this line of precedent on AAE’s asserted
First Amendment interests.

    Even if prejudice were not apparent, an acute tension in
interests presents an inescapable risk of prejudice to the
opposing party. We therefore adopt the precautionary
principle when deciding a motion to join a party midstream:
unless the interests of the party to be joined align with those
26            BAIN V. CALIF. TEACHERS ASS’N

of the original party to the suit, then, as a general rule, the
proper course is to deny the motion. See Spangler v.
Pasadena City Bd. of Educ., 552 F.2d 1326, 1328 (9th Cir.
1977) (Kennedy, J.) (adding a party under Rule 21 is only
appropriate where the party seeking joinder, among other
things, “offer[s] all the same reasons for relief”). The
impropriety of granting a Rule 21 motion under the
circumstances here is magnified where, as here, adding a
party seeks to cure a jurisdictional defect. Anaheim,
190 F.3d at 999, 1001 (granting a Rule 21 motion to cure a
jurisdictional defect is “rare” and must be “‘exercised
sparingly’” (quoting Newman-Green, 490 U.S. at 837)).

     To be sure, the Unions, acting in their capacities as the
exclusive bargaining representatives of California’s public
school teachers in negotiations with the State, offer
privileges of membership that AAE cannot provide. These
include voting rights within the Unions and the privilege of
serving on certain school district policy committees. This
disjuncture in benefits may provide some surface appeal to
AAE’s argument that their members might join the Unions
but for the Unions’ mandatory political fees, and thus that
their members and Plaintiffs share a common interest in this
litigation. But AAE fails to identify any of its members that
seek to join the Unions. And even if it did, voting rights and
committee privileges do not implicate a First Amendment
interest. Minn. State Bd. for Comm’y Colleges v. Knight,
465 U.S. 271, 289–90 (1984). That is because “pressure to
join the exclusive representative in order to give
[individuals] the opportunity to,” among other things, “serve
on . . . committees” is “inherent in our system of
government; it does not create an unconstitutional inhibition
               BAIN V. CALIF. TEACHERS ASS’N                      27

on associational freedom.” 7 Id. (emphasis added). Thus,
whatever the merits of Plaintiffs’ First Amendment claim,
their constitutional interest does not extend to the collective
bargaining rights that are peculiar to an agency shop union.

    In sum, because AAE’s interests in pursuing this appeal
diverge from those of the original Plaintiffs, the risk of
prejudice to the Unions of adding AAE as a party to
Plaintiffs’ action is acute. AAE therefore cannot satisfy the
three-part test for joining a party under Rule 21.

                        CONCLUSION

    In both the district court and in their merits briefing on
appeal, Plaintiffs were the only plaintiffs to this suit. But
Plaintiffs resigned their Union memberships during the
pendency of their appeal, thereby mooting the appeal and
depriving us of jurisdiction. Now, at the eleventh hour,
Plaintiffs seek to add a new party, AAE, to their action.
Adding a new party on appeal is rarely done, however, and
is particularly ill-advised—indeed, we hold it to be
erroneous as a matter of law—when used to resurrect a moot
case. Fox, 42 F.3d at 144; see also Jacobs, 420 U.S. at 129–
30. And even if mootness were not an insurmountable
barrier to considering a Rule 21 motion, we would still deny
the motion because AAE fails to satisfy the criteria for Rule
21 joinder. Accordingly, we DISMISS Plaintiffs’ appeal




    7
      Knight involved a challenge to a state statute requiring public
employers to engage in official exchanges of views only with an
“exclusive representative” of the public employee union’s bargaining
unit. Knight, 465 U.S. at 273.
28               BAIN V. CALIF. TEACHERS ASS’N

and REMAND 8 to the district court with instructions to
dismiss the case without vacating its judgment. 9




     8
      In line with our disposition, we GRANT the Unions’ motion to
dismiss the appeal as moot and DENY Plaintiffs and AAE’s motion for
joinder.

     9
       The Unions argue for dismissal without vacatur and Plaintiffs do
not offer a counterargument. We agree with the Unions that vacating the
district court’s judgment would be inconsistent with the “equitable
tradition of vacatur.” U.S. Bancorp Mortg. Co. v. Bonner Mall P’ship,
513 U.S. 18, 25 (1994). “It is [Plaintiffs’] burden, as the part[ies] seeking
relief from the status quo of the appellate judgment, to demonstrate . . .
equitable entitlement to the extraordinary remedy of vacatur.
[Plaintiffs’] voluntary forfeiture of review,” by being the parties
responsible for mooting the controversy, “constitutes a failure of equity
that makes the burden decisive . . . .” Id. at 26. Indeed, allowing
Plaintiffs to vacate the judgment below would constitute a “refined form
of collateral attack” that would “disturb the orderly operation of the
federal judicial system.” Id. at 27.
