                 FOR PUBLICATION

  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

ALLIED CONCRETE AND SUPPLY               No. 16-56546
CO., a California corporation;
CALPORTLAND COMPANY, a                     D.C. No.
California Corporation; GARY            CV 16-4830 RGK
BALE REDI-MIX CONCRETE, INC., a
California corporation; HOLLIDAY
ROCK CO., INC., a California
corporation; NATIONAL READY
MIXED CONCRETE CO., a
California corporation;
ROBERTSON’S READY MIX, LTD., a
California limited partnership;
SPRAGUES ROCK AND SAND
COMPANY, a California
corporation; SUPERIOR READY MIX
CONCRETE L.P.,
                Plaintiffs-Appellees,

                 v.

CHRISTINE BAKER, in her official
capacity as the Director of the
Department of Industrial Relations
of the State of California; JULIE A.
SU, in her official capacity as
Labor Commissioner of the State
of California, Division of Labor
Standards Enforcement,
                         Defendants,
2        ALLIED CONCRETE AND SUPPLY V. IBT

INTERNATIONAL BROTHERHOOD OF
TEAMSTERS,
  Intervenor-Defendant-Appellant.


ALLIED CONCRETE AND SUPPLY               No. 17-55343
CO., a California corporation;
CALPORTLAND COMPANY, a                     D.C. No.
California Corporation; GARY            CV 16-4830 RGK
BALE REDI-MIX CONCRETE, INC., a
California corporation; HOLLIDAY
ROCK CO., INC., a California
corporation; NATIONAL READY
MIXED CONCRETE CO., a
California corporation;
ROBERTSON’S READY MIX, LTD., a
California limited partnership;
SPRAGUES ROCK AND SAND
COMPANY, a California
corporation; SUPERIOR READY MIX
CONCRETE L.P.,
                Plaintiffs-Appellees,

                 v.

CHRISTINE BAKER, in her official
capacity as the Director of the
Department of Industrial Relations
of the State of California; JULIE A.
SU, in her official capacity as
Labor Commissioner of the State
of California, Division of Labor
Standards Enforcement,
             Defendants-Appellants.
         ALLIED CONCRETE AND SUPPLY V. IBT             3

ALLIED CONCRETE AND SUPPLY              No. 17-55503
CO., a California corporation;
CALPORTLAND COMPANY, a                    D.C. No.
California Corporation; GARY           CV 16-4830 RGK
BALE REDI-MIX CONCRETE, INC., a
California corporation; HOLLIDAY
ROCK CO., INC., a California              OPINION
corporation; NATIONAL READY
MIXED CONCRETE CO., a
California corporation;
ROBERTSON’S READY MIX, LTD., a
California limited partnership;
SPRAGUES ROCK AND SAND
COMPANY, a California
corporation; SUPERIOR READY MIX
CONCRETE L.P.,
              Plaintiffs-Appellants,

                 v.

CHRISTINE BAKER, in her official
capacity as the Director of the
Department of Industrial Relations
of the State of California; JULIE A.
SU, in her official capacity as
Labor Commissioner of the State
of California, Division of Labor
Standards Enforcement,
              Defendants-Appellees.
4           ALLIED CONCRETE AND SUPPLY V. IBT

        Appeals from the United States District Court
            for the Central District of California
         R. Gary Klausner, District Judge, Presiding

             Argued and Submitted March 7, 2018
                    Pasadena, California

                     Filed September 20, 2018

       Before: A. Wallace Tashima, Richard A. Paez,
         and Jacqueline H. Nguyen, Circuit Judges.

                    Opinion by Judge Tashima


                            SUMMARY*


                             Labor Law

   The panel affirmed in part and reversed in part the district
court’s judgment and remanded in an action brought by a
group of ready-mix concrete suppliers, challenging California
Labor Code § 1720.9, which amended California’s prevailing
wage laws to include delivery drivers of ready-mix concrete.

    The district court denied a motion of the International
Brotherhood of Teamsters (“IBT”) to intervene on the side of
the State to defend the law, and it granted the State’s motion
to dismiss plaintiffs’ claim that § 1720.9 was preempted by
the Federal Aviation Administration Authorization Act. The

    *
      This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
           ALLIED CONCRETE AND SUPPLY V. IBT                   5

district court granted summary judgment in favor of plaintiffs
on their claim that § 1720.9 violated the Equal Protection
Clause of the Fourteenth Amendment, ruling that, under the
rational basis test, there were no legally relevant differences
between ready-mix drivers and other delivery drivers;
therefore, the State did not have any legitimate justification
for singling out the ready-mix suppliers.

    Reversing the district court’s grant of summary judgment
in favor of plaintiffs on their equal protection claim, the panel
concluded that the district court wrongly disregarded as
irrelevant certain differences between ready-mix drivers and
other drivers that the legislature could have relied on in
extending the prevailing wage law. The panel explained that
the California Supreme Court has stated that prevailing wage
laws further goals such as: (1) generally protecting
employees on public works projects, (2) benefitting the public
through the superior efficiency of well-paid employees, and
(3) permitting union contractors to compete with nonunion
contractors. The panel held that the legislature could have
rationally concluded that extending the prevailing wage law
to ready-mix drivers ahead of other drivers would further
these respective goals because ready-mix drivers: (1) are
more integrated into the construction process than other
materials drivers and should be paid accordingly; (2) are
more skilled than other drivers and provide a material that is
more important to public works projects than other materials
such that paying the prevailing wage will attract superior
drivers and improve public works; and (3) are more likely to
be unionized and, therefore, vulnerable to underbidding.

    Reversing the district court’s denial of IBT’s motion to
intervene, the panel held that the union had a significantly
protectable interest at stake in the case. The panel concluded
6         ALLIED CONCRETE AND SUPPLY V. IBT

that IBT’s appeal was not moot in light of the reversal on the
equal protection claim.

    The panel affirmed the district court’s dismissal of
plaintiffs’ claim of FAAAA preemption because the
prevailing wage law was not related to prices, routes, and
services within the meaning of the FAAAA’s preemption
clause.


                        COUNSEL

Ken Lau (argued), Assistant Chief Counsel; Christopher
Jagard, Chief Counsel; Office of the Director—Legal Unit,
Department of Industrial Relations, Oakland, California;
John J. Korbol and Mi Kim, Counsel, Office of the
Director—Legal Unit, Department of Industrial Relations,
Los Angeles, California; for Defendants-Appellants/Cross-
Appellees.

Michael G. Yoder (argued) and Christopher S. Whittaker,
O’Melveny & Myers LLP, Newport Beach, California; Anton
Metlitsky, O’Melveny & Myers LLP, New York, New York;
for Plaintiffs-Appellees/Cross-Appellants.

Scott A. Kronland (argued), Stacey M. Leyton, and Eric P.
Brown, Altshuler Berzon LLP, San Francisco, California, for
Intervenor-Defendant-Appellant/Amicus Curiae.

Kerry Shapiro, Jon Wilner, and Matthew J. Sanders, Jeffer
Mangels Butler & Mitchell LLP, San Francisco, California,
for Amicus Curiae California Construction and Industrial
Materials Association.
           ALLIED CONCRETE AND SUPPLY V. IBT                  7

                          OPINION

TASHIMA, Circuit Judge:

   California’s general prevailing wage laws ensure that
workers employed on public works projects are paid a
minimum wage. In 2015, California amended the prevailing
wage laws to include delivery drivers of ready-mix concrete.
Cal. Lab. Code § 1720.9.

    A group of ready-mix concrete suppliers (collectively,
“Plaintiffs”) challenged § 1720.9, alleging that it violated the
Equal Protection Clause of the Fourteenth Amendment to the
United States Constitution (“equal protection claim”) and that
the Federal Aviation Administration Authorization Act of
1994 (“FAAAA”) preempted the state law. The International
Brotherhood of Teamsters (“IBT”) moved to intervene on the
side of the State to defend the law.

    The district court denied IBT’s motion to intervene and
granted the State’s motion to dismiss Plaintiffs’ FAAAA
preemption claim. However, the district court granted
Plaintiffs’ summary judgment motion on the equal protection
claim, concluding that § 1720.9 did not pass muster under the
rational basis test. The court reasoned that there were no
legally relevant differences between ready-mix drivers and
other delivery drivers; therefore, the State did not have any
legitimate justification for singling out the ready-mix
suppliers.

    We conclude that the district court wrongly disregarded
as irrelevant certain differences between ready-mix drivers
and other drivers that the legislature could have relied on in
extending the prevailing wage law. We thus reverse the
8         ALLIED CONCRETE AND SUPPLY V. IBT

district court’s grant of summary judgment in favor of
Plaintiffs and order the court to enter judgment on behalf of
Defendants. Likewise, we hold that IBT had a significantly
protectable interest at stake in the case and we reverse the
district court’s denial of IBT’s motion for leave to intervene.
On the FAAAA preemption question, we affirm the district
court’s dismissal of Plaintiffs’ claim.

                       BACKGROUND

1. Prevailing Wage Laws and California Labor Code
   § 1720.9

    California’s prevailing wage law establishes the minimum
wage that workers employed on “public works” must receive.
See Cal. Lab. Code §§ 1720, 1771. “Public works” is
generally defined as construction or related work, done under
contract, and paid for in any part out of public funds. Id.
§ 1720(a)(1). The California Supreme Court has described
the purpose of the general prevailing wage law:

       The overall purpose of the prevailing wage
       law . . . is to benefit and protect employees on
       public works projects. This general objective
       subsumes within it a number of specific goals:
       to protect employees from substandard wages
       that might be paid if contractors could recruit
       labor from distant cheap-labor areas; to permit
       union contractors to compete with nonunion
       contractors; to benefit the public through the
       superior efficiency of well-paid employees;
       and to compensate nonpublic employees with
       higher wages for the absence of job security
          ALLIED CONCRETE AND SUPPLY V. IBT                  9

       and employment benefits enjoyed by public
       employees.

Lusardi Constr. Co. v. Aubry, 824 P.2d 643, 649 (Cal. 1992).

    The California Director of Industrial Relations (the
“Director”) publishes the prevailing wage rates and enforces
the law by collecting payroll (and other related) records from
employers. Cal. Lab. Code §§ 1771.4, 1776. Further, when
there is a question about the applicability of the prevailing
wage law, the Director determines “whether a specific project
or type of work is a public work.” Id. at § 1773.5(b); see also
id. § 1773(c) (establishing administrative appeal process).
When there is a dispute, courts may also review whether a
worker is entitled to prevailing wages. See, e.g., Williams v.
SnSands Corp., 67 Cal. Rptr. 3d 606 (Ct. App. 2007); O.G.
Sansone Co. v. Dep’t of Transp., 127 Cal. Rptr. 799 (Ct. App.
1976). Courts and the Director both ask whether the worker’s
task was “functionally related to the process of construction,”
and “an integrated aspect of the ‘flow’ process of
construction.” O.G. Sansone, 127 Cal. Rptr. at 804; see also
A&A Ready Mix Concrete, Public Works Case No. 99-037
(Dep’t of Indus. Relations Apr. 10, 2000).

    On October 10, 2015, Governor Edmund G. Brown, Jr.,
signed AB 219, which amended California’s prevailing wage
law by adding Labor Code §1720.9. It provides that “public
works” include “the hauling and delivery of ready-mixed
concrete to carry out a public works contract” regardless of
who employs the driver or whether the driver is delivering
from a dedicated batch plant. Cal. Lab. Code § 1720.9.
Therefore, all ready-mix drivers delivering to public works
must be paid prevailing wages. Before adopting the final bill,
the California Legislature considered a version of AB 219
10           ALLIED CONCRETE AND SUPPLY V. IBT

that would have required payment of prevailing wages to
asphalt delivery drivers as well, but ultimately limited the
expansion to ready-mix concrete drivers.

    Ready-mix concrete is defined as “concrete that is
manufactured in a factory or a batching plant, according to a
set recipe, and then delivered in a liquefied state by mixer
truck for immediate incorporation into a project.” Id.
§ 1720.9(b). Its ingredients are prepared and mixed at a
concrete plant. Production of concrete is time-sensitive
because concrete begins to set quickly after water is added.
Ready-mix is delivered in specialized trucks with a rotating
tank. Id. Drivers of ready-mix trucks control the amount of
water added to the rotating tank and the speed at which the
tank spins, meaning that they can alter the nature of the
concrete.1 By contrast, even though asphalt delivery may also
be time-sensitive, drivers transport asphalt in dump trucks,
rather than mixing trucks, and drivers cannot alter the asphalt
once it is in the truck. For certain projects, such as paving
roads, asphalt and ready-mix are interchangeable, for others,
such as building walls and other structural supports, the
materials are not substitutes.

2. Procedural Background

   On June 30, 2016, Plaintiffs filed a complaint against the
Director and the Labor Commissioner of the State of
California (collectively, the “State”).2 The Complaint alleged


     1
     The ready-mix drivers do not always have discretion to decide how
much water to add, but must follow instructions from engineers.
     2
       Plaintiffs also sued Governor Brown, but later dismissed the case as
to him.
            ALLIED CONCRETE AND SUPPLY V. IBT                        11

that § 1720.9 violates the Equal Protection Clause of the
Constitution, or alternatively, is preempted by the FAAAA,
and sought injunctive and declaratory relief. Before the State
answered the complaint, IBT moved for leave to intervene,
either as of right or permissively. See Fed. R. Civ. P. 24(a) &
(b). On August 22, 2016, Plaintiffs sought a preliminary
injunction on their equal protection claim. Before the court
ruled on Plaintiffs’ motion for injunctive relief, the State
moved to dismiss under Federal Rule of Civil Procedure
12(b)(6).

    Subsequently, in September, the district court denied
IBT’s motion to intervene, reasoning that: (1) the union
could not intervene by right because it did not have a
significantly protectable interest in the case; and (2) that the
union could not permissively intervene because it would
cause a delay and the State could protect any interests IBT
may have. IBT appealed the denial of its motion to intervene.

    On October 18, 2016, the district court granted Plaintiffs’
motion for a preliminary injunction on the equal protection
claim, finding that § 1720.9 was not likely to survive rational
basis review.3 In December, the district court granted the
State’s motion to dismiss Allied Concrete’s FAAAA claim,
but denied the motion as to the equal protection claim. Allied
Concrete appealed the dismissal of its FAAAA claim.

   Thereafter, Plaintiffs moved for summary judgment and
requested that the temporary injunction be made permanent.
The district court, holding that § 1720.9 violated the Equal
Protection Clause, permanently enjoined the statute’s

     3
       The State appealed the preliminary injunction, but the subsequent
entry of the permanent injunction mooted that appeal.
12        ALLIED CONCRETE AND SUPPLY V. IBT

application and enforcement. First, the district court defined
the classification in § 1720.9 as treating “ready-mixed
concrete drivers differently than other materials drivers.”
And, although the district court credited the State’s evidence
as to the differences between ready-mix drivers and drivers
of other materials, it concluded – without explanation – that
those differences were immaterial because “all that matters
for inclusion in the [prevailing wage law] is whether or not
drivers are hauling and delivering construction materials to
public works sites.” Thus, the district court concluded that
“in all respects relevant to the [prevailing wage law], ready-
mixed concrete drivers and other materials drivers are
similarly situated.” Recognizing that the State’s interests
may be legitimate, the district court nevertheless struck down
the statute because the classification was “arbitrary” and not
rationally related to any of the interests. The State appealed.

                  STANDARD OF REVIEW

    We review de novo grants of summary judgment and
dismissals. First Resort, Inc. v. Herrera, 860 F.3d 1263,
1271 (9th Cir. 2017), cert. denied, 138 S. Ct. 2709 (2018); Ah
Quin v. Cty. of Kauai Dep’t of Transp., 733 F.3d 267, 270
(9th Cir. 2013).

    We consider de novo whether a motion to intervene of
right should have been granted, Canatella v. California,
404 F.3d 1106, 1112 (9th Cir. 2005), and, if necessary,
review for abuse of discretion a denial of permissive
intervention, id. at 1117.
           ALLIED CONCRETE AND SUPPLY V. IBT                 13

                         DISCUSSION

1.     Equal Protection

    The parties agree that the rational basis test applies.
Therefore, § 1720.9 “cannot run afoul of the Equal Protection
Clause if there is a rational relationship between the disparity
of treatment and some legitimate governmental purpose.”
Heller v. Doe, 509 U.S. 312, 320 (1993). Non-suspect
classifications are

       constitutionally valid if there is a plausible
       policy reason for the classification, the
       legislative facts on which the classification is
       apparently based rationally may have been
       considered to be true by the governmental
       decisionmaker, and the relationship of the
       classification to its goal is not so attenuated as
       to render the distinction arbitrary or irrational.

Armour v. City of Indianapolis, 566 U.S. 673, 681 (2012)
(internal quotation marks omitted); see also Johnson v.
Rancho Santiago Cmty. Coll. Dist., 623 F.3d 1011, 1031 (9th
Cir. 2010) (“[A] state action need not actually further a
legitimate interest; it is enough that the governing body
‘could have rationally decided that’ the action would further
that interest.” (quoting Minnesota v. Clover Leaf Creamery
Co., 449 U.S. 456, 466 (1981))). “Further, because the
classification is presumed constitutional, the burden is on the
[party] attacking the legislative arrangement to negative every
conceivable basis which might support it.” Armour, 566 U.S.
at 681 (internal quotation marks omitted); see also Clover
Leaf Creamery Co., 449 U.S. at 464 (“[P]arties challenging
legislation under the Equal Protection Clause . . . cannot
14           ALLIED CONCRETE AND SUPPLY V. IBT

prevail so long as it is evident from all the considerations
presented to [the legislature], and those of which we may take
judicial notice, that the question is at least debatable.”
(second alteration in original ) (internal quotation marks and
citations omitted)); Vance v. Bradley, 440 U.S. 93, 111
(1979) (“[T]hose challenging the legislative judgment must
convince the court that the legislative facts on which the
classification is apparently based could not reasonably be
conceived to be true by the governmental decisionmaker.”).

    We disagree with the district court’s conclusion that the
differences between ready-mix drivers and other delivery
drivers is immaterial for the purposes of the prevailing wage
law. As mentioned above, the California Supreme Court has
stated that prevailing wage laws further goals such as:
(1) generally protecting employees on public works projects,
(2) benefitting the public through the superior efficiency of
well-paid employees, and (3) permitting union contractors to
compete with nonunion contractors. See Lusardi, 824 P.2d at
649. The legislature could have rationally concluded that
extending the prevailing wage law to ready-mix drivers ahead
of other drivers would further these respective goals because
ready-mix drivers: (1) are more integrated into the
construction process than other materials drivers and should
be paid accordingly; (2) are more skilled than other drivers
and provide a material that is more important to public works
projects than other materials such that paying the prevailing
wage will attract superior drivers and improve public works;
and (3) are more likely to be unionized and, therefore,
vulnerable to underbidding.4 Plaintiffs have not met their



    4
      Each of these justifications is alone sufficient to survive the rational
basis test. The State and IBT present us with several other potential
             ALLIED CONCRETE AND SUPPLY V. IBT                            15

high burden of convincing us that these legislative facts
“could not reasonably be conceived to be true by the
governmental decisionmaker.” Bradley, 440 U.S. at 111.
The legislative facts are at least debatable and the
classification rationally related to furthering the purposes of
the prevailing wage law; as such, the statute survives the
rational basis test.5 See FCC v. Beach Commc’ns, Inc.,
508 U.S. 307, 320 (1993).

    A. Benefit Employees on Public Works Projects

     First, “[t]he overall purpose of the prevailing wage law
. . . is to benefit and protect employees on public works
projects.” Lusardi, 824 P.2d at 649. In extending the
prevailing wage law to benefit ready-mix drivers, the
legislature could have rationally decided that the delivery of
ready-mix to a public work is part of the “flow of
construction” and should be compensated as such. Not only
would this protect the ready-mix drivers, but if the legislature
believed that the ready-mix drivers were actually more
integrated in construction, the payment of prevailing wages



justifications, but we need not reach those and offer no opinion on whether
they would save the challenged statute.
    5
       Undergirding our analysis is the idea that the legislature is permitted
to act incrementally in dealing with perceived problems. See City of New
Orleans v. Dukes, 427 U.S. 297, 303 (1976) (per curiam) (“Legislatures
may implement their program step by step in such economic areas,
adopting regulations that only partially ameliorate a perceived evil and
deferring complete elimination of the evil to future regulations.” (citations
omitted)); see also Ry. Express Agency v. New York, 336 U.S. 106, 110
(1949) (“It is no requirement of equal protection that all evils of the same
genus be eradicated or none at all.” (citing Cent. Lumber Co. v. South
Dakota, 226 U.S. 157, 160 (1912))).
16        ALLIED CONCRETE AND SUPPLY V. IBT

could increase efficiency in public works projects by
attracting higher-skilled workers.

    Specifically, the legislature could have concluded that the
ready-mix drivers are more integrated into the flow of
construction because they bring a perishable commodity to a
construction site, and, in certain instances, need to
incorporate it immediately. During legislative hearings on
the bill, an IBT representative testified:

       These workers are part of the construction
       process. That’s what’s different and unique
       about this from any other material coming to
       the job site. You can . . . it’s not dumping a
       load of lumber or a bag of nails or whatever
       and leaving. They bring this
       commodity—which is perishable—and [it]
       has to be incorporated immediately and the
       driver participates in the incorporation process
       with the workers. They are part of it. They
       move the truck. They operate levers and
       equipment that moves the concrete and the
       rate of flow in conjunction with the
       construction workers. They are integral to the
       process.

At least some of the legislators were impressed by this
perceived difference from other materials. As one legislator
stated: “I will be supporting the bill today. I do get the
distinction between the product we’re talking about and
delivering in effect, dumping a delivery of pipes or paint or
steel. This is a different commodity.”
          ALLIED CONCRETE AND SUPPLY V. IBT                 17

    The conclusion that ready-mix drivers are more integral
to the public works projects than other drivers because of the
material’s properties and the driver’s tasks is rational on its
face. Therefore, it is up to Plaintiffs to negate this
justification as inconceivable. Plaintiffs attempt this through
three arguments. They first argue that the delivery of ready-
mix is not any different than that of other materials. For
example, one contractor stated that “[f]rom [his] perspective
as a contractor, there is no meaningful difference between the
delivery of ready-mixed concrete . . . and the delivery of any
other construction material . . . . Approximately 95% of the
time, all of the [ready-mix] goes into a single pump that [his]
employees than [sic] use to place the concrete.” While this
argument raises a factual dispute with the testimony from
IBT’s witness, quoted above, it does not significantly weigh
against the legislature conceivably concluding that ready-mix
drivers are more important to the construction process based
on the properties of the materials, the uniqueness of the
trucks, and the driver’s responsibilities upon arrival. The
legislature, where there is no suspect class at issue, has wide
leeway to consider different, and potentially competing, facts.
See Armour, 566 U.S. at 685 (“[T]he Constitution does not
require the [government] to draw the perfect line nor even to
draw a line superior to some other line it might have drawn.
It requires only that the line actually drawn be a rational
line.”).

    Next, Plaintiffs argue that the legislature could not
rationally conclude that ready-mix drivers were more
integrated into the flow of construction than other drivers
because the Director had previously found that the drivers
were not always entitled to prevailing wages under the pre-
§ 1720.9 test. In A&A Ready Mix Concrete, the Director
concluded that ready-mix drivers delivering the material, but
18         ALLIED CONCRETE AND SUPPLY V. IBT

not performing on-site construction work, were not part of the
flow of construction. Plaintiffs argue that this administrative
ruling undercuts any factual basis for the legislature to have
decided otherwise. This argument fails for several reasons.
First and foremost, the legislature is not bound to accept the
findings of an administrative agency. Legislatures frequently
change laws in response to administrative (or judicial)
decisions with which they do not agree. As such, this
decision of the agency is of little relevance to our analysis.

    Finally, Plaintiffs argue that extending the prevailing
wage to all ready-mix drivers is overbroad because not all
ready-mix drivers are sufficiently integral to the flow of
construction. For example, Plaintiffs contend that not all
drivers incorporate the ready-mix, and that even if they do,
this would not necessarily support higher wages for the drive
time. Again, Plaintiffs question where the legislature drew
the line. But, for the reasons stated above, the legislature
could have rationally concluded that ready-mix drivers were
more integral to public works than other drivers and that the
drive time – when the driver controls the rate of rotation and
the amount of water in the drum – is part of the construction.

     B. Ensure Superior Projects

    Second, another goal of the prevailing wage law is to
“benefit the public through the superior efficiency of well-
paid employees.” Lusardi, 824 P.2d at 649. The State offers
that the legislature may have decided that the unique aspects
of a ready-mix driver’s job, and the nature of ready-mix as a
material for structural projects such as buildings, bridges, and
dams (as opposed to roads), make the quality of ready-mix
drivers more important to public works projects than other
drivers. This argument rests on two premises that Plaintiffs
           ALLIED CONCRETE AND SUPPLY V. IBT                 19

challenge:     (1) that ready-mix drivers have unique
responsibilities that are more important to the success of a
public works project; and (2) that ready-mix is more often
used in “structural” projects.

    As to the first premise, there are clear differences between
ready-mix drivers and other materials drivers relevant to the
equal protection analysis. Ready-mix drivers use specialized
trucks, with a rotating mixing drum, whereas asphalt drivers
use dump trucks. Ready-mix drivers can change the
consistency of their load by adding water to the mixture or
altering the speed of rotation of the drum. Further, ready-mix
drivers require more training than asphalt drivers and must
carry a different driver’s license endorsement than asphalt
drivers. It is conceivable that the legislature could have
rationally believed these facts, determined that ready-mix
drivers need more skills than other drivers, and concluded
that prevailing wages would attract higher-quality workers.

    Plaintiffs argue that there is no meaningful difference
between the delivery of ready-mix and other materials. For
example, some contractors declare that ready-mix and asphalt
drivers both merely drop the material where the contractors’
employees tell the driver to dump it. Plaintiffs further argue
that both ready-mix and asphalt have a limited duration in
which they must be delivered. Finally, Plaintiffs argue that
even though the ready-mix driver has the ability to add water
to the mixture, he or she does not have discretion to do so.
Instead, the drivers simply follow instructions from
somebody else.

    Nonetheless, the different licensing requirements and the
ability of ready-mix drivers to control the cement in their
trucks are rational grounds for distinguishing between them
20         ALLIED CONCRETE AND SUPPLY V. IBT

and other drivers. Further, even if ready-mix drivers do not
have discretion to add water to the mixture, or change the
speed of the rotating drum, they still must control these
variables during the drive, which is not true for drivers of
typical dump trucks.          Carefully following important
instructions is itself a valuable skill.

    As to the second premise, although it is true that many
projects could interchange the materials depending on cost,
there is evidence that ready-mix is used for structural support,
such as walls or footings, more often than other materials. By
contrast, asphalt cannot be used as a structural material, and
is most often used for paving. It is easy to imagine a
legislator concluding that a failed structure, such as a dam or
bridge, is worse than a poorly-paved road. Therefore, the
legislature could have rationally concluded that ready-mix is
more important to sensitive public works and that the drivers
must be more skilled to ensure the integrity of the material
they deliver.

    Again, Plaintiffs cannot negate this justification. Aside
from arguing that ready-mix drivers are not any different than
other drivers, Plaintiffs also contend that concerns about
structural projects do not survive constitutional scrutiny
because not all public works are structural projects. But this
argument cannot carry the day under rational basis review.
See Heller, 509 U.S. at 321 (“[C]ourts are compelled under
rational-basis review to accept a legislature’s generalizations
even when there is an imperfect fit between means and
ends.”).
          ALLIED CONCRETE AND SUPPLY V. IBT                 21

   C. Protect From Underbidding

    Third, another purpose of the prevailing wage law is “to
permit union contractors to compete with nonunion
contractors.” Lusardi, 824 P.2d at 649. The district court,
citing Merrifield v. Lockyer, 547 F.3d 978, 991 n.15 (9th Cir.
2008), however, rejected this argument: “[L]egislation
passed for the sole purpose of protecting union employers
from non-union competition will not pass constitutional
muster.” As we further explain below, Merrifield does not
support the district court’s conclusion. True, bare economic
protectionism is not a valid justification for discriminatory
treatment, but the interest in protecting union workers from
underbidding conceivably is about ensuring a certain standard
of worker – and avoiding a race to the bottom – rather than
granting favors to politically important actors. See O.G.
Sansone, 127 Cal. Rptr. at 813–14 (describing the
maintenance of competition between union and non-union
workers as one of the purposes of the federal prevailing wage
law); see also Indep. Roofing Contractors v. Dep’t of Indus.
Relations, 28 Cal. Rptr. 2d 550, 557 (Ct. App. 1994)
(recognizing the “declared public policy of [California] in
favor of collective bargaining”).

    The State argues that the legislature could have rationally
concluded that ready-mix drivers were more vulnerable
to underbidding than other drivers because a higher
percentage of ready-mix drivers are union workers. An IBT
representative estimates that 95% of ready-mix drivers in the
San Francisco area are working under collective bargaining
agreements (“CBAs”), whereas “IBT has only one or two
[CBAs] with contractors who are also commercial suppliers
covering asphalt delivery in California.” If unionized ready-
mix drivers were underbid by a non-union supplier, 95% of
22         ALLIED CONCRETE AND SUPPLY V. IBT

drivers in San Francisco would be ineligible for the job.
Therefore, it seems reasonable that the legislature could have
rationally believed that underbidding in the ready-mix market
is more harmful and that § 1720.9 would further the interest
in preventing underbidding.

    Plaintiffs respond that underbidding by non-union drivers
may be a problem, regardless of the material carried, and that
the state has not provided any evidence that the disparity
between union and non-union rates is greater for ready-mix
drivers than other drivers. These arguments miss the mark.
Just because underbidding may be an issue for drivers of
other materials does not mean that the legislature could not
have rationally concluded that the problem was more acute
for ready-mix drivers due to their higher unionization rates.
Second, the state is not required to produce empirical
evidence to support the statute; it is Plaintiffs’ burden is to
negate conceivable justifications. See Beach Commc’ns,
508 U.S. at 315 (“[A] legislative choice . . . may be based on
rational speculation unsupported by evidence or empirical
data.”).

     D. Not Bare Economic Protectionism

    Plaintiffs contend that they have refuted all of the State’s
justifications and that the only explanation for § 1720.9 is that
the legislature wanted to protect the suppliers of other
materials from competition. Plaintiffs, however, have put
forward no evidence that the legislature engaged in improper
favoritism, and the Ninth Circuit cases that Plaintiffs cite are
inapposite.

   Plaintiffs rely on Merrifield for the premise that
“economic protectionism for the sake of economic
          ALLIED CONCRETE AND SUPPLY V. IBT                 23

protectionism is irrational with respect to determining if a
classification survives rational basis review.” 547 F.3d at 991
n.15. Merrifield, however, presented a unique set of facts
distinguishable from those here. In Merrifield, a pest-control
professional who did not use pesticides challenged, on due
process grounds, the application of California’s overall
pesticide licensing scheme to him and other non-pesticide
users. Id. at 987. We rejected the due process claim,
reasoning that the state had a public safety interest in
“requiring persons who do not use pesticides to learn about
the risks of pesticides . . . because persons like [plaintiff]
work in environments where they may be exposed to
pesticides that have been applied previously and left on-site.”
Id. at 988.

    The plaintiff in Merrifield also challenged, on equal
protection grounds, the exemptions in the licensing scheme,
which exempted pest-control professionals who dealt with
bats, raccoons, skunks, and squirrels and did not use
pesticides from the licensing requirement, but did not
similarly exempt professionals who worked with mice, rats,
or pigeons. Id. at 981–82. Applying the rational basis test,
we struck down these selective exemptions. Id. at 991. We
reasoned that the classification in the licensing scheme did
not survive constitutional muster because it contradicted the
very interest the State proffered to defeat the due process
claim – public health concerns about exposure to pesticide.
See id. (“We cannot simultaneously uphold the licensing
requirement under due process based on one rationale and
then uphold [plaintiff’s] exclusion from the exemption based
on a completely contradictory rationale.”). The rationale was
contradictory because those pest-control operators who
worked with bats, rats, racoons, skunks, and squirrels were
more at risk of being exposed to pesticides even if they did
24         ALLIED CONCRETE AND SUPPLY V. IBT

not themselves use pesticides than similarly-situated
operators who dealt with more-common pests like mice or
rats. Id. at 991.

    Plaintiffs also rely on Fowler Packing Co. v. Lanier,
844 F.3d 809, 816 (9th Cir. 2016). In Fowler Packing, we
concluded, on a motion to dismiss, that plaintiffs had pleaded
an equal protection claim because the only conceivable
explanation for a portion of the challenged legislation was the
need to win the political support of a particular labor union.
Id. at 816. The legislation at issue in Fowler Packing
“created a ‘safe harbor’ that gave employers an affirmative
defense against” certain minimum wage claims. Id. at 811.
However, there were carve outs from the safe harbor that only
benefitted the labor union which had ongoing suits against
employers. Id. at 815. These carve outs came in the form of
cut-off dates that corresponded almost exactly to the filing
dates of the labor union’s cases against certain employers. Id.
Accepting the plaintiffs’ allegations as true, we held that they
had alleged enough to survive a motion to dismiss.

    Both cases are easily distinguishable from the situation
here. Unlike in Merrifield, there is no suggestion that
classifying ready-mix drivers as distinct from other drivers
actually contradicts the purposes of the prevailing wage law.
Similarly, there is no specific evidence like the cut-off dates
in Fowler Packing that clearly suggests improper favoritism.
Plus, the burden on Plaintiffs here to come forward with
evidence that negates every conceivable basis for the law is
much higher than that of the Fowler Packing plaintiffs
opposing a motion to dismiss.

   Finally, Plaintiffs emphasize the fact that asphalt was
dropped from an earlier version of § 1720.9 as a sign that the
           ALLIED CONCRETE AND SUPPLY V. IBT                 25

law’s only justification is to protect ready-mix suppliers’
competitors. Without more, the fact that the legislature once
considered including asphalt in the legislation is not evidence
of improper motive. In fact, considering asphalt, but then
removing it after holding hearings, could just as easily bolster
the conclusion that after reviewing the facts, the legislature
reached an informed judgment.

    Because Plaintiffs have not negated every conceivable
justification for § 1720.9, we conclude that the statute passes
the rational basis test and does not violate the Equal
Protection Clause.

2. Intervention

    In a separate appeal, IBT challenges the district court’s
denial of its motion for leave to intervene as of right or by
permission. During oral argument, we raised the issue of
whether IBT’s appeal would be moot if we reversed the
district court on the equal protection claim. IBT argued that
its appeal would not be moot because Plaintiffs could still
move for rehearing en banc or petition for a writ of certiorari
with the Supreme Court.

    We are not aware of any decision from our Circuit that
addresses whether a potential petition for rehearing or
certiorari keeps a case alive for the purposes of appealing a
motion to intervene. The typical rule is that “[a]n appeal is
moot if there exists no present controversy as to which
effective relief can be granted.” W. Coast Seafood
Processors Ass’n v. Natural Res. Def. Council, Inc., 643 F.3d
701, 704 (9th Cir. 2011) (internal quotation marks omitted);
see also United States v. Ford, 650 F.2d 1141, 1143 (9th Cir.
1981). On the other hand, where the district court has entered
26           ALLIED CONCRETE AND SUPPLY V. IBT

judgment, but a party has appealed some aspect of the case,
an appeal of the motion to intervene is not moot. See
Canatella, 404 F.3d at 1109 n.1. We think that the situation
here is more similar to Canatella than West Coast Seafood or
Ford. In both West Coast Seafood and Ford, the underlying
litigation had concluded; here, as IBT points out, Plaintiffs
may pursue their case by filing a petition for rehearing or
rehearing en banc here, or by petitioning the Supreme Court
for a writ of certiorari.6 We therefore hold that IBT’s appeal
is not moot in light of our reversal and will reach the district
court’s decision denying intervention. See U.S. Postal Serv.
v. Brennan, 579 F.2d 188, 190 n.1 (2d Cir. 1978) (“Because
application for rehearing has been filed and the time to
petition for certiorari has not expired, the case has not
reached final judgment, and the issue of intervention is not
moot.” (citation omitted)).

    To determine whether a party may intervene as of right,
we employ a four-part test: (1) the motion must be timely;
(2) the applicant must claim a “significantly protectable
interest” in the action; (3) the disposition of the action must
as a practical matter impair or impede the applicant’s ability
to protect that interest; and (4) the applicant’s interest may be
inadequately represented by the other parties. Wilderness
Soc’y v. U.S. Forest Serv., 630 F.3d 1173, 1177 (9th Cir.
2011) (en banc).

    We have previously considered a motion for IBT to
intervene on the side of the State to defend California’s
prevailing wage law.      See Californians for Safe &


     6
     Plaintiffs have already indicated that they intend to file a petition for
rehearing en banc challenging this Circuit’s FAAAA preemption
precedent.
          ALLIED CONCRETE AND SUPPLY V. IBT                 27

Competitive Dump Truck Transp. v. Mendonca, 152 F.3d
1184, 1189–90 (9th Cir. 1998). Because the facts of
Mendonca are almost identical to this case, we follow its
reasoning and reverse the district court’s denial of IBT’s
motion to intervene.

    In Mendonca, “public works contractors who provide[d]
transportation-related services on publicly-funded projects”
challenged California’s prevailing wage laws, arguing that the
FAAAA preempted the state law. Id. at 1185–86. We
affirmed the district court’s grant of IBT’s motion to
intervene, reasoning that: (1) IBT’s motion was timely;
(2) IBT’s members had a “‘significant interest’ in receiving
the prevailing wage for their services as opposed to a
substandard wage”; (3) “IBT’s members’ right to receive the
prevailing wage” would have been impaired had plaintiffs
prevailed; and (4) IBT demonstrated that the State’s
representation of its interests may have been inadequate
“because the employment interests of IBT’s members were
potentially more narrow and parochial than the interests of
the public at large.” Id. at 1189–90.

    The district court attempted to distinguish Mendonca by
emphasizing that we used the phrase “receive the prevailing
wage” in Mendonca. Id. at 1190 (emphasis added). By
emphasizing the word “receive,” the district court assumed
that the IBT members in Mendonca would not have been paid
the prevailing wage if the statute were struck down. Here, on
the other hand, the district court relied on the fact that many
IBT members already received the prevailing wage pursuant
to CBAs – regardless of the prevailing wage law. In other
words, the district court concluded that the IBT members
“would merely lose § 1720.9 as a statutory backstop to their
[CBAs].”
28          ALLIED CONCRETE AND SUPPLY V. IBT

    Mendonca is not susceptible to the district court’s narrow
reading. Moreover, we are not convinced that the distinction
between receiving a prevailing wage pursuant to statute and
maintaining the statutory right to receive a wage is a
meaningful one for purposes of assessing standing to
intervene. For one, Mendonca makes no mention of
distinguishing IBT members by whether they actually
received the prevailing wage or not, and there is no
discussion about whether certain IBT members were already
paid the prevailing wage under CBAs. It is entirely possible
that the members at issue in Mendonca were subject to CBAs.
For another, the district court just as easily could have
emphasized the word “right” in the statement “[if plaintiffs]
prevailed, it would have clearly impaired IBT’s members’
right to receive the prevailing wage” and come to the
opposite conclusion. Id. at 1190. In any event, we do not see
a significant difference either way, even if the Mendonca
intervenors were not subject to CBAs. For example,
receiving a prevailing wage in the absence of a CBA might
technically be different than receiving it pursuant to a
contract, but for the purposes of a significantly protectable
interest, we think they are indistinguishable. Even if all of
IBT’s members are subject to CBAs7 that pay them the
prevailing wage, a statutory right to that wage is still
important and not at all speculative. CBAs are not
permanent, and re-negotiating about wages from a statutory
floor is certainly a much better bargaining position than
starting from scratch. Maintaining the statutory floor is a
significant, protectable interest for IBT.




    7
      IBT alleges that there are times when some of its members are not
protected by CBAs.
            ALLIED CONCRETE AND SUPPLY V. IBT                         29

    Likewise, Mendonca guides us on the other three
elements of intervention by right. First, there is no dispute
that IBT’s motion was timely. Next, because IBT has an
interest in the right to a prevailing wage, the district court
invalidating the law clearly impaired that interest. Id. And,
finally, IBT’s interests are potentially more narrow than the
public’s at large, and the State’s representation of those
interests “may have been inadequate.” Id. (emphasis added).

    As such, we see no reason to depart from Mendonca and
therefore conclude that the district court erred in denying
IBT’s motion to intervene as a matter of right.8

3. Preemption

     The district court correctly dismissed Plaintiffs’ FAAAA
preemption claim. The prevailing wage law “is not ‘related
to’ . . . prices, routes, and services within the meaning of the
[FAAAA’s] preemption clause.” Mendonca, 152 F.3d at
1189; see also Dilts v. Penske Logistics, LLC, 769 F.3d 637,
647–48 (9th Cir. 2014) (reaffirming Mendonca). Thus,
preemption does not apply.

                            CONCLUSION

    The district court’s summary judgment in favor of
Plaintiffs’ equal protection claim, and its denial of IBT’s
motion for leave to intervene as of right are REVERSED.
We AFFIRM the district court’s dismissal of Plaintiffs’




     8
       Because we uphold IBT’s intervention as a matter of right, we need
not reach its alternative motion for permissive intervention.
30        ALLIED CONCRETE AND SUPPLY V. IBT

FAAAA preemption claim. We REMAND to the district
court to enter judgment consistent with this opinion.

   The State Defendants and IBT shall recover their costs on
appeal from Plaintiffs.
