                  FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

PATRICIA SANFORD,                       
                 Plaintiff-Appellant,
                  v.
MEMBERWORKS, INC., a Delaware
corporation, aka MWI Essentials,
aka MWI Home and Garden, aka
MWI Connections, aka MWI                      No. 05-55175
Valuemax; WEST CORPORATION, a
Delaware corporation; WEST                     D.C. No.
                                            CV-02-00601-LAB
TELEMARKETING CORPORATION, a
Delaware corporation,                          OPINION
              Defendants-Appellees,
                  v.
PRESTON SMITH; RITA SMITH, on
behalf of themselves and all others
similarly situated,
  Plaintiffs-Intervenors-Appellants.
                                        
        Appeal from the United States District Court
          for the Southern District of California
         Larry A. Burns, District Judge, Presiding

                  Argued and Submitted
          February 9, 2007—Pasadena, California

                     Filed April 16, 2007

 Before: Cynthia Holcomb Hall, Diarmuid F. O’Scannlain,
        and Consuelo M. Callahan, Circuit Judges.

                   Opinion by Judge Hall

                             4265
4268            SANFORD v. MEMBERWORKS, INC.


                         COUNSEL

Eric Alan Isaacson, Lerach Coughlin Stoia Geller Rudman &
Robbins, San Diego, California, for the plaintiff-appellant and
the plaintiffs-intervenors-appellants.
                   SANFORD v. MEMBERWORKS, INC.                      4269
Darrel J. Hieber, Skadden, Arps, Slate, Meagher & Flom, Los
Angeles, California, for defendant-appellee Memberworks,
Inc.

M. Jerome Elmore and Joshua F. Thorpe, Bondurant, Mixson
& Elmore, Atlanta, Georgia, for defendants-appellees West
Corporation and West Telemarketing Corporation.


                                OPINION

HALL, Senior Circuit Judge:

   Patricia Sanford appeals the district court’s order confirm-
ing an arbitration award in her action against MemberWorks,
Inc., West Corporation, and West Telemarketing Corporation
for alleged violations of 39 U.S.C. § 3009 and related state
law claims. Preston and Rita Smith appeal the district court’s
order denying their motion to intervene in the same action.
The district court had jurisdiction under 28 U.S.C. § 1331.
This court has jurisdiction under 28 U.S.C. § 1291. We affirm
in part, vacate in part, and remand for further proceedings.

                           I.   Background

   In response to a television advertisement, Sanford pur-
chased a set of fitness tapes by phone from NCP Marketing,
through a call center operated by defendants West Corpora-
tion and West Telemarketing Corporation (collectively
“West”). At the time, defendant MemberWorks, Inc. had an
agreement with NCP under which NCP’s sales agent, West,
would read customers a sales script for a free trial member-
ship in the MemberWorks Essentials program.1 The script was
identical or substantially similar to the following:
  1
    Essentials is a service which offers its members a 20% discount at cer-
tain retailers for an annual fee of $72.
4270               SANFORD v. MEMBERWORKS, INC.
      Mr(s). ___, for purchasing Tae-Bo today, we’re
      sending you a risk-FREE 30-day membership to
      ESSENTIALS, a service designed to SAVE YOU
      20% from leading stores such as EXPRESS and
      FLORSHEIM, plus reward savings at VICTORIA’S
      SECRET, TJ MAXX, PIER ONE and TARGET,
      PLUS additional savings on eyewear, beauty prod-
      ucts, haircuts, and more! After 30 days, the service
      is extended to a full year for just $6 a month, billed
      annually in advance to the credit card you’re using
      today. If you want to cancel, just call the toll-free
      number that appears in your kit in the first 30 days
      and YOU WON’T BE BILLED. So look for that kit
      in the mail, OKAY?

   According to MemberWorks records, Sanford was enrolled
in the Essentials program and was sent a membership kit with
an agreement containing an arbitration clause.2 Sanford has no
recollection of having been read a script, agreeing to the trial
membership, or receiving a membership kit. When Sanford
did not cancel at the end of the trial membership, her credit
card was billed $72 for a one-year membership. The follow-
ing year, Sanford was charged $84 for renewal of the pro-
gram, which Sanford disputed and which MemberWorks then
refunded. Sanford claims this second charge is the first she
heard of the Essentials program.3

   On March 28, 2002, Sanford filed a claim against Member-
Works and West for violating 39 U.S.C. § 3009, which makes
the mailing of unordered merchandise an unfair trade practice,
  2
     The arbitration clause, nestled in a paragraph entitled “Governing
Law,” states that “[a]ny dispute arising between You and Us will be
resolved by submission to arbitration in Fairfield County, State of Con-
necticut, in accordance with the rules of the American Arbitration Associ-
ation then in effect.”
   3
     During this action, MemberWorks also refunded the initial $72 charge
to Sanford.
                 SANFORD v. MEMBERWORKS, INC.                 4271
along with state law claims for conversion, unjust enrichment,
and fraud. The complaint sought class certification and a jury
trial. MemberWorks then brought a motion (which West
joined) to compel arbitration of Sanford’s individual claim
pursuant to the arbitration clause of the membership agree-
ment, to stay the case pending arbitration or alternatively to
dismiss for failure to state a claim, and to strike the class alle-
gations. Sanford disputed that she had entered a contract with
MemberWorks and argued that the arbitration clause was
therefore not binding upon her.

  On July 15, 2002, the district court granted MemberWorks’
motion to compel arbitration. The court’s order acknowledged
Sanford’s contention that she was unaware that she had
enrolled in the Essentials program. But it explained that
because Sanford “challenges the validity of the whole contract
and not specifically the arbitration agreement,” her claim “is
an issue for the arbitrator and not the Court.” The district
court then denied MemberWorks’ request for a stay and
denied the motion to strike as moot.

   Because West did not allege it was a party to any agree-
ment with Sanford, the court denied West’s joinder in the
motion to compel arbitration. Instead it dismissed the federal
claim against West on the ground that West never mailed San-
ford any unordered merchandise, and it declined to exercise
supplemental jurisdiction over the state law claims against
that defendant. As a result, the court explained, the case was
“terminated as to West.” The court further explained that if
the arbitration were not completed within twelve months, the
court would terminate the remainder of the case.

  Sanford then brought a Petition to Arbitrate her class-action
complaint before the American Arbitration Association,
which appointed an arbitrator. In a preliminary ruling, the
arbitrator ruled that he lacked jurisdiction to certify a class
because he interpreted the district court’s order as compelling
arbitration only of Sanford’s individual claim, not the issue of
4272             SANFORD v. MEMBERWORKS, INC.
class certification. Sanford then moved the district court to
reconsider the order compelling arbitration and to certify a
class. The district court denied this motion on June 12, 2003,
explaining that the July 2002 order compelled Sanford to arbi-
trate only her individual claim and dismissed the class claims
as moot. Sanford then brought a second motion for reconsid-
eration, relying upon the intervening decision Green Tree
Financial Corp. v. Bazzle, 539 U.S. 444 (2003), which held
that the issue of whether a contract permits class arbitration
is a question for the arbitrator, not the court. The district court
denied this motion as well, explaining that Sanford “has had
the opportunity to request class arbitration of the arbitrator”
and lost.

   On March 15, 2004, the arbitrator issued his final ruling.
Initially, he held that he lacked jurisdiction to decide San-
ford’s contention that no contract was formed between the
parties. Calling his situation “curious,” the arbitrator
explained that the question of contract formation must be
determined by the court before compelling arbitration under
that contract. Because the district court had compelled arbitra-
tion here, he reasoned, it must necessarily have found that a
contract existed. The arbitrator’s jurisdiction stems from the
district court’s order, so he determined he was powerless to
revisit that ruling.

   But when purporting to decide Count I of Sanford’s peti-
tion (seeking restitution for mailing unordered merchandise in
violation of Section 3009), the arbitrator then found no con-
tract had been formed. The arbitrator held that “even if the
script was read to [Sanford,] the basic requirements of ‘offer’
and ‘acceptance’ were not met.” He therefore awarded San-
ford $72 in damages plus $34.57 in interest and $21,209.28
in arbitration fees, offset by the $72 reimbursement Member-
Works had recently paid Sanford. The arbitrator found for
MemberWorks on Sanford’s other claims.

  The Smiths then filed a motion to intervene in the district
court to serve as alternative class plaintiffs. Shortly thereafter,
                SANFORD v. MEMBERWORKS, INC.                4273
MemberWorks moved the district court to confirm the arbitra-
tor’s award. Sanford moved to confirm the arbitrator’s deci-
sion that no contract was formed, but otherwise to vacate the
award. On December 30, 2004, the district court denied San-
ford’s and the Smiths’ motions, and granted MemberWorks’
motion to confirm the arbitration award.

                  II.   Standards of Review

   We review de novo a district court’s order compelling arbi-
tration, its dismissal of the class claims as moot, and its dis-
missal of the claims against West. See Circuit City Stores,
Inc. v. Adams, 279 F.3d 889, 892 n.2 (9th Cir. 2002); Gest v.
Bradbury, 443 F.3d 1177, 1181 n.1 (9th Cir. 1996); Warshaw
v. Xoma Corp., 74 F.3d 955, 957 (9th Cir. 1996). Our review
of the arbitration award is more deferential: we will vacate the
award only if the arbitrator violated the Federal Arbitration
Act or if the award itself is “completely irrational” or exhibits
“manifest disregard of the law.” Coutee v. Barington Capital
Group, L.P., 336 F.3d 1128, 1132 (9th Cir. 2003) (internal
citation omitted). The denial of a motion to intervene as
untimely is reviewed for abuse of discretion. Smith v. Marsh,
194 F.3d 1045, 1049 (9th Cir. 1999).

                        III.   Discussion

A.   Waiver

   Before discussing the merits of Sanford’s appeal, we must
address defendants’ claim that Sanford waived her right to
challenge the July 2002 order. In separate motions to dismiss
in part, MemberWorks and West assert that the July 2002
order compelling arbitration was an appealable final order
under the Federal Arbitration Act. Therefore, they assert, San-
ford should have immediately appealed that order, and any
4274               SANFORD v. MEMBERWORKS, INC.
appeal now is untimely under Federal Rule of Appellate Pro-
cedure 4.4

   We begin by noting that through the Federal Arbitration
Act, Congress sought “to move the parties to an arbitrable dis-
pute out of court and into arbitration as quickly and easily as
possible.” Bushley v. Credit Suisse First Boston, 360 F.3d
1149, 1153 (9th Cir. 2004) (internal citations omitted). To that
end, the act generally “promote[s] appeals from orders barring
arbitration and limit[s] appeals from orders directing arbitra-
tion.” Id.; see also 9 U.S.C. § 16(b)(2) (“[A]n appeal may not
be taken from an interlocutory order . . . directing arbitration
to proceed.”). Defendants invoke an exception to this rule, 9
U.S.C. § 16(a)(3), which permits an immediate appeal of a
“final decision with respect to an arbitration.”

   [1] The Supreme Court interpreted this statutory text in
Green Tree Financial Corp.—Alabama v. Randolph, 531 U.S.
79 (2000). Randolph addressed the appealability of an order
compelling arbitration and dismissing plaintiff’s underlying
claims with prejudice. The Court held that the statutory phrase
“final decision” should be accorded the “well-established
meaning” that governs appealability under 28 U.S.C. § 1291:
a decision is final if it “ends the litigation on the merits and
leaves nothing more for the court to do but execute the judg-
ment.” Id. at 86. In that case, “the District Court ha[d] ordered
the parties to proceed to arbitration, and dismissed all the
claims before it.” Id. at 89. Because the order “disposed of the
  4
   Defendants also seek to dismiss Sanford’s appeal to the extent that it
challenges the court’s order denying the Smiths’ motion to intervene, and
the Smiths’ appeal to the extent that it challenges rulings other than the
denial of intervention. We decline to reach these alternative arguments.
Even assuming defendants are correct, either Sanford or the Smiths has
standing to appeal each issue presented. Cf. Estate of Bishop v. Bechtel
Power Corp., 905 F.2d 1272, 1275 (9th Cir. 1990) (“Because [the attor-
ney] has not pursued an appeal of his own, we must decide whether a
party has standing to appeal an order of sanctions against its attorney.”)
(emphasis added).
                  SANFORD v. MEMBERWORKS, INC.                   4275
entire case on the merits and left no part of it pending before”
the district court, the Court held that the order was final and
therefore appealable. Id. at 86.

   [2] We have addressed the post-Randolph divide between
appealable and non-appealable orders compelling arbitration
in a trio of cases. In Interactive Flight Technologies, Inc. v.
Swissair Swiss Air Transport Co., 249 F.3d 1177, 1179 (9th
Cir. 2001), we held that an order granting defendant’s motion
to compel arbitration and dismissing the action without preju-
dice constitutes an appealable final decision. By contrast, in
Dees v. Billy, 394 F.3d 1290, 1292-93 (9th Cir. 2005) we
found that an order compelling arbitration and staying the
case was not immediately appealable. Dees explained that this
order was not final, despite the fact that the court ordered the
case “administratively closed,” because “the trial court here
did not dismiss [plaintiff’s] claim.” Id. at 1292. The district
court had compelled arbitration of the plaintiff’s malpractice
claim, but its failure to dismiss the claim meant that “that
claim—although currently stayed—remains before the trial
court.” Id. at 1293. Similarly, in Bushley, 360 F.3d at 1153,
we found an order that compelled arbitration without ruling
on defendant’s motion to stay or dismiss the claim is not
“final and appealable” because the action was “effectively
stayed pending the conclusion of the [ ] arbitration.”

   [3] Applying these principles to the case at bar yields the
inescapable conclusion that the July 2002 order was not a
“final decision with respect to an arbitration.” While the order
compelled Sanford to arbitrate her claims against Member-
Works, the district court did not dismiss those claims. Rather,
the court stated that it would terminate the case “if the arbitra-
tion . . . is not completed within twelve months.”5 In a later
order, the district court made clear that no final judgment had
been issued for purposes of permitting an appeal under Sec-
  5
  By comparison, the order explicitly dismissed Sanford’s claim against
West, and noted that “the case shall be terminated as to West.”
4276               SANFORD v. MEMBERWORKS, INC.
tion 1291.6 Defendants point out that no “live” claims
remained before the court, which later explained that it would
only entertain motions relating to the arbitrator’s final award.
But this posture is no different than that presented in Dees,
where the case was “administratively closed” pending the
results of arbitration. Dees, 394 F.3d at 1292. Because San-
ford’s claims were not dismissed, they “remain[ed] before the
trial court,” id. at 1292, and at most could be described as “ef-
fectively stayed pending the conclusion of the [ ] arbitration,”
Bushley, 360 F.3d at 1153.

   [4] We therefore conclude that the July 2002 order was not
a “final decision with respect to the arbitration,” and San-
ford’s appeal of that order now is timely. See Am. Ironworks
& Erectors, Inc. v. N. Am. Const. Corp., 248 F.3d 892, 897
(9th Cir. 2001) (“An interlocutory order becomes appealable
when final judgment is entered.”).7

B.     The 2002 Order Compelling Arbitration

  [5] It is axiomatic that “[a]rbitration is a matter of contract
and a party cannot be required to submit any dispute which
he has not agreed so to submit.” AT&T Tech., Inc. v.
  6
     After the district court denied Sanford’s motion for reconsideration,
Sanford moved the court for a final judgment so that she could appeal the
order compelling arbitration. In an October 2003 order, the district court
refused to do so. Under a bold heading entitled “No Final Judgment,” the
court “decline[d] to issue a Final Judgment at this time. There has been
no motion by Defendants to dismiss this case due to expiration of the arbi-
tration period, and thus Plaintiff’s request for a final judgment is prema-
ture.”
   7
     MemberWorks asserts for the first time at oral argument that Sanford’s
appeal of the dismissal of the class allegations as moot is untimely under
Fed. R. Civ. P. 23(f). Assuming without deciding that the rule applies,
“[n]othing within the language of the Rule 23(f), its authorizing statute (28
U.S.C. § 1292(e)), or its history indicates that it is meant to provide the
exclusive route to obtaining appellate review or to impose time limits on
[ ] appeals proper under other statutory provisions.” Bates v. United Par-
cel Serv., 465 F.3d 1069, 1076 n.5 (9th Cir. 2006).
                   SANFORD v. MEMBERWORKS, INC.                        4277
Commc’n Workers of Am., 475 U.S. 643, 648 (1986). As a
result, when one party disputes “the making of the arbitration
agreement,” the Federal Arbitration Act requires that “the
court [ ] proceed summarily to the trial thereof” before com-
pelling arbitration under the agreement. 9 U.S.C. § 4. We
have interpreted this language to encompass not only chal-
lenges to the arbitration clause itself, but also challenges to
the making of the contract containing the arbitration clause.
Three Valleys Mun. Water Dist. v. E.F. Hutton & Co., 925
F.2d 1136, 1140-41 (9th Cir. 1991). Issues regarding the
validity or enforcement of a putative contract mandating arbi-
tration should be referred to an arbitrator, but challenges to
the existence of a contract as a whole must be determined by
the court prior to ordering arbitration. Id.8

   [6] The parties here do not dispute that Sanford challenged
the existence of a contract with MemberWorks, and therefore
under Three Valleys the district court was required to rule
upon the contract formation issue before compelling arbitra-
tion. Their quarrel regards whether the district court in fact
did so. Sanford claims that the district court misinterpreted
Three Valleys and therefore inappropriately referred the con-
tract formation issue to the arbitrator. MemberWorks
responds that, while the district court did not explicitly find
that a contract was formed, the July 2002 order should be
understood as implicitly having decided this question.

   MemberWorks asserts that the July 2002 order was prem-
ised on the finding of a contract due to “the authorities upon
which it relied to support its holding.” Citibank, N.A. v. Wells
  8
    Although the Supreme Court has not yet spoken on this issue, it has
specifically noted the distinction between the validity of the contract and
the question whether any agreement was formed. See Buckeye Check
Cashing, Inc. v. Cardegna, 126 S. Ct. 1204, 1208 n.1 (2005). The Court
explained that while its ruling relegated the question of contract illegality
to the arbitrator, it “does not speak to the issue decided in the cases cited
by respondents . . . which hold that it is for courts to decide whether the
alleged obligor ever signed the contract.” Id.
4278            SANFORD v. MEMBERWORKS, INC.
Fargo Asia Ltd., 495 U.S. 660, 669-70 (1990). The order cor-
rectly stated that it must determine “whether a valid agree-
ment to arbitrate exists” and cited Three Valleys at one point,
indicating that the court was familiar with the decision. There-
fore, MemberWorks argues, it would be unreasonable to con-
strue the 2002 order as having referred the contract formation
question to the arbitrator.

   [7] MemberWorks’ argument is unpersuasive. The 2002
order could not have implicitly decided the question of con-
tract formation; it explicitly refused to decide the question.
The operative language from the order reads:

    Under the FAA, the court is limited to determining
    (1) whether a valid agreement to arbitrate exists, and,
    if it does, (2) whether the agreement encompasses
    the dispute at issue. A party challenging the validity
    of the contract, as a whole, is a question for the arbi-
    trator and not the Court. Prima Paint Corp. v. Flood
    & Conklin Mfg. Co., 388 U.S. 395 (1967). The hold-
    ing in Prima Paint extends to attempts to rescind
    contracts on other grounds. Three Valleys Mun.
    Water Dist. v. E.F. Hutton & Co., 925 F.2d 1136,
    1140 (9th Cir. 1991). Therefore, a plaintiff must
    challenge the arbitration agreement itself.

    Here, Plaintiff contends that she was not aware that
    she was part of the membership program until she
    canceled in February 2000. In essence, she chal-
    lenges the validity of the contract and not specifi-
    cally the arbitration agreement. Accordingly, this is
    an issue for the arbitrator and not the court. (Quota-
    tion marks and citations omitted).

The order did not decide that the parties formed a contract.
Rather, it interpreted Prima Paint as mandating that the court
decide all challenges to an arbitration clause but the arbitrator
decide all challenges to the contract as a whole. We rejected
                   SANFORD v. MEMBERWORKS, INC.                      4279
this argument in Three Valleys, which limited Prima Paint “to
challenges seeking to avoid or rescind a contract—not to
challenges going to the very existence of a contract that a
party claims never to have agreed to.” Three Valleys, 925
F.2d at 1140 (emphasis in original). The district court’s lone
citation to Three Valleys thus misconstrues that case: the
order claims that Three Valleys extended Prima Paint, when
in fact it limited Prima Paint by precluding its application to
the very issue that Sanford presented to the district court.9

   [8] The 2002 order clearly stated that “Plaintiff’s conten[-
tion] that she was not aware that she was part of the member-
ship program” was a “challenge[ to] the validity of the whole
contract” and “[a]ccordingly [ ] is an issue for the arbitrator
and not the Court.” This holding is erroneous under Three
Valleys. We must therefore vacate the July 2002 order com-
pelling arbitration and remand the case to the district court to
determine whether a contract was formed between Sanford
and MemberWorks.
  9
    Defendants also assert that a finding of contractual formation was
appropriate because Sanford failed to offer evidence rebutting Member-
Works’ motion to compel arbitration. Even assuming that Rule 56 proce-
dures are applicable to a motion to compel, but cf. Hamilton v. Shearson-
Lehman Am. Exp., Inc., 813 F.2d 1532, 1535 (9th Cir. 1987), we cannot
say that the evidence MemberWorks proffered in support of its motion
shows the absence of a genuine issue of material fact. MemberWorks
introduced a declaration that its business records indicated that Sanford
was enrolled in the Essentials program and sent a membership kit, along
with copies of the kit and of MemberWorks’ sales script. As Sanford notes
(and the arbitrator subsequently found), this evidence could be interpreted
as supporting her claim that MemberWorks’ practices were misleading
and that no assent ever occurred. “The district court, when considering a
motion to compel arbitration which is opposed on the ground that no
agreement to arbitrate had been made between the parties, should give to
the opposing party the benefit of all reasonable doubts and inferences that
may arise.” Three Valleys, 925 F.2d at 1141 (citation omitted). We there-
fore decline to find that MemberWorks has demonstrated the absence of
a material fact on the issue of contract formation.
4280               SANFORD v. MEMBERWORKS, INC.
C.     Class Allegations

   [9] Sanford also claims that the July 2002 order erred in
limiting arbitration to her individual claim and dismissing her
class allegations as moot.10 She relies primarily upon the
Supreme Court’s intervening decision in Green Tree Finan-
cial Corp. v. Bazzle, 539 U.S. 444 (2003), which held that the
question whether a contract permits class arbitration is an
issue for the arbitrator to decide. We do not reach the merits
of this argument. Because we vacate the order compelling
arbitration of Sanford’s individual claim on other grounds, the
class allegations are no longer moot. On remand, Sanford
shall be permitted to seek relief on a class-wide basis. See
DeMando v. Morris, 206 F.3d 1300, 1303 (9th Cir. 2000)
(reviving plaintiff’s motion for class certification when dispo-
sition of appeal renders motion “no longer moot”).

D.     Dismissal of Claims Against West

   Sanford also challenges the district court’s dismissal of her
claims against West. Her federal claim was brought under 39
U.S.C. § 3009, which prohibits “the mailing of unordered
merchandise.” 39 U.S.C. § 3009(a); see also id. § 3009(c)
(preventing “the mailer of any merchandise mailed in viola-
tion of subsection (a)” from billing for such merchandise).
The district court dismissed Sanford’s Section 3009 claim
against West on the ground that West never actually mailed
any merchandise to her. Sanford does not dispute this factual
finding. Rather, she argues that “mailing” should be inter-
preted broadly, to include those who cause an item to be
mailed.
  10
     After compelling arbitration of Sanford’s dispute with MemberWorks,
the 2002 order denied as moot MemberWorks’ motion to strike class alle-
gations. In its June 2003 order denying reconsideration, the district court
clarified that its earlier order had compelled arbitration of Sanford’s indi-
vidual claim and had dismissed Sanford’s class allegations as moot.
                 SANFORD v. MEMBERWORKS, INC.                  4281
   [10] This broad interpretation cannot be reconciled with the
plain language of the statute. Section 3009 is part of the Chap-
ter 30 of the Postal Reorganization Act, PL 91-375 (1970),
entitled “Nonmailable Matter.” Other provisions of this stat-
ute plainly seek to reach those who cause prohibited matter to
be mailed, in addition to the party actually mailing the mate-
rial. See, e.g., 39 U.S.C. § 3008(a) (“Whoever for himself, or
by his agents or assigns, mails or causes to be mailed any pan-
dering advertisement . . . shall be subject to an order of the
Postal Service to refrain from further mailings . . . .” ); id.
§ 3010(a) (“Any person who mails or causes to be mailed any
sexually oriented advertisement shall place on the envelope or
cover thereof his name and address as the sender thereof and
such mark or notice as the Postal Service may prescribe.”). By
contrast, Section 3009 reaches only “the mailing of unordered
merchandise.”

   [11] “Where Congress includes particular language in one
section of a statute but omits it in another . . . , it is generally
presumed that Congress acts intentionally and purposely in
the disparate inclusion or exclusion.” Keene Corp. v. United
States, 508 U.S. 200, 208 (1993) (internal citation and quota-
tion marks omitted). Congress’s use of the phrase “causes to
be mailed” in other sections of Chapter 30, but its omission
in Section 3009, indicates that this section was not intended
to reach beyond those who actually mail unordered merchan-
dise. Accordingly, we agree with the district court’s ruling
that Section 3009 does not reach West, and affirm the dis-
missal of Sanford’s federal claim against that defendant. In
light of this holding, it was not an abuse of discretion to dis-
miss Sanford’s state law claims against West without preju-
dice once the federal claim was dismissed. See United Mine
Workers v. Gibbs, 383 U.S. 715 (1966).

E.   The Smiths’ Motion to Intervene

 The Smiths challenge the district court’s denial of their
motion to intervene as untimely. The timeliness of interven-
4282            SANFORD v. MEMBERWORKS, INC.
tion is measured by “(1) the stage of the proceeding at which
an applicant seeks to intervene; (2) the prejudice to other par-
ties; and (3) the reason for the length of the delay.” United
States v. Carpenter, 298 F.3d 1122, 1125 (9th Cir. 2002)
(internal citation omitted). Here, the district court found that
the Smiths waited nearly two years after the class claims were
dismissed, and that intervention now, after Sanford’s individ-
ual claims had been arbitrated, would be prejudicial to Mem-
berWorks.

   [12] Without ruling on the propriety of this decision, we
note that the district court’s concerns are no longer present in
light of our vacatur of the order compelling arbitration and
dismissing the class allegations as moot. We therefore vacate
the denial of the Smiths’ motion to intervene and permit the
district court to re-evaluate this motion anew in light of our
holding today.

                      IV.   Conclusion

   For the reasons discussed above, we DENY defendants’
motions to dismiss this appeal in part. We AFFIRM the dis-
trict court’s dismissal of the claims against West, but other-
wise VACATE the July 2002 order compelling arbitration of
Sanford’s claims against MemberWorks and dismissing San-
ford’s class allegations as moot. We thus necessarily
VACATE the district court’s 2003 orders regarding Sanford’s
motions for reconsideration, and the 2004 order confirming
the arbitration award and denying the Smiths’ motion to inter-
vene. Finally, we REMAND the case for further proceedings
in accordance with this opinion. Each party shall bear its own
costs on appeal.
