          United States Court of Appeals
                     For the First Circuit
No. 16-2052

                     AES PUERTO RICO, L.P.,

                      Plaintiff, Appellant,

                               v.

 MARCELO TRUJILLO-PANISSE, in his Official Capacity as Mayor of
  the Municipality of Humacao; MUNICIPALITY OF HUMACAO; WALTER
   TORRES-MALDONADO, in his Official Capacity as Mayor of the
       Municipality of Peñuelas; MUNICIPALITY OF PEÑUELAS,

                     Defendants, Appellees.


          APPEAL FROM THE UNITED STATES DISTRICT COURT
                 FOR THE DISTRICT OF PUERTO RICO

         [Hon. Francisco A. Besosa, U.S. District Judge]


                             Before

                  Torruella, Lipez, and Barron,
                          Circuit Judges.

     Peter D. Keisler, with whom Ricardo L. Ortiz-Colón, Fiddler
González & Rodríguez, P.S.C., David T. Buente, Samuel B. Boxerman,
Paul J. Zidlicky, Christopher A. Eiswerth, and Sidley Austin LLP
were on brief, for appellant.
     Francisco José Medina-Medina, with whom Pedro E. Ortiz-
Álvarez, LLC was on brief, for appellees.
     John F. Cooney, Douglas H. Green, Margaret K. Fawal, and
Venable LLP on brief for amici curiae the Utility Solid Waste
Activities Group and the American Coal Ash Association.


                          May 16, 2017
           LIPEZ, Circuit Judge.         This case requires us to decide

whether two Puerto Rico municipalities may prohibit the beneficial

use and disposal of coal ash at landfills within their borders

even though a state agency has authorized such activities at those

particular landfills.     Appellant AES Puerto Rico, L.P. ("AES-PR"),

a coal-fired power plant owner, claims that the two municipal

ordinances    banning   the   approved    handling    of   "coal       combustion

residuals" ("CCRs") are preempted by federal and Commonwealth law

and also violate various provisions of the United States and Puerto

Rico constitutions.      The district court granted summary judgment

for the municipalities on AES's federal claims and declined to

exercise jurisdiction over the Commonwealth claims.

           After    careful   review,     we   conclude     that       the   local

ordinances may not be enforced to the extent they directly conflict

with   Commonwealth     law   as   promulgated       by    the    Puerto     Rico

Environmental Quality Board ("EQB"). Hence, we reverse the summary

judgment in favor of the municipalities and remand with directions

to the district court to enter judgment for AES-PR based on its

claim of Commonwealth law preemption.

                                    I.

             We begin by examining the legal framework that governs

the disposal of CCRs in Puerto Rico.            That multi-tiered scheme

consists     of   (1)   federal    law,    specifically,         the     Resource

Conservation and Recovery Act of 1976 ("RCRA"), 42 U.S.C. §§ 6901-


                                   - 2 -
6992k; (2) the Commonwealth's Environmental Public Policy Act,

P.R. Laws Ann. tit. 12, §§ 8001-8007f, the source of the EQB's

authority; and (3) the Autonomous Municipalities Act, P.R. Laws

Ann.    tit.    21,        §§    4001-4008,    4051-4058,        the    source   of   the

municipalities' authority.                 We briefly describe each in turn, as

pertinent to our analysis.

A. Federal Law: RCRA

       Congress enacted RCRA, "a comprehensive environmental statute

that governs the treatment, storage, and disposal of solid and

hazardous waste," based, inter alia, on its finding that waste

disposal       had     become         a   national     problem     requiring     federal

involvement.         Meghrig v. KFC W., Inc., 516 U.S. 479, 483 (1996);

see 42 U.S.C. § 6901(a)(4); 42 U.S.C. § 6901(a)(2) (noting the

"rising tide of scrap, discarded, and waste materials").                         Despite

the perceived need for federal action, however, Congress affirmed

in RCRA that "the collection and disposal of solid wastes should

continue to be primarily the function of State, regional, and local

agencies."           Id.    §    6901(a)(4).      Hence,    RCRA       anticipates    that

federal, state, and local governments will work cooperatively to

ensure the safe and environmentally appropriate management of

solid   waste,        and       the   statute's      objectives    expressly     include

establishment of "a viable Federal-State partnership" to "promote

the protection of health and the environment and to conserve

valuable material and energy resources."                   Id. § 6902(a)(7), (a).


                                            - 3 -
           This cooperative approach applies both to "hazardous

wastes"   under   RCRA   subtitle    C,     id.   §§   6921-6939g,   and   to

nonhazardous solid waste under RCRA subtitle D, id. §§ 6941-6949a.

See City of Chicago v. Envtl. Def. Fund, 511 U.S. 328, 331 (1994).

The federal Environmental Protection Agency ("EPA") has classified

CCRs as nonhazardous waste, see 40 C.F.R. § 261.4(b)(4)(i), and,

accordingly, they are regulated under subtitle D. 1           With respect

to such materials, Congress sought to promote methods of disposal


     1 In a May 2000 Regulatory Determination, the EPA reaffirmed
its earlier conclusion that coal combustion wastes should not be
regulated as hazardous waste and "decided that it is appropriate
to establish national regulations under non-hazardous waste
authorities for coal combustion wastes that are disposed in
landfills and surface impoundments."        Notice of Regulatory
Determination on Wastes from the Combustion of Fossil Fuels, 65
Fed. Reg. 32,214, 32,221, 32,229 (May 22, 2000), 2000 WL 642307.
However, the EPA also stated that regulation was "not warranted"
for most of the beneficial uses of coal combustion wastes, such as
waste stabilization and use in construction products.       Id. at
32,214, 32,221.
       Ten years later, the EPA announced that it was again
considering whether to regulate CCRs under subtitle C "when they
are destined for disposal in landfills or surface impoundments,"
or to "regulate disposal of such materials under subtitle D of
RCRA by issuing national minimum criteria." Hazardous and Solid
Waste Management System; Identification and Listing of Special
Wastes; Disposal of Coal Combustion Residuals From Electric
Utilities, 75 Fed. Reg. 35,128 (June 21, 2010), 2010 WL 2470432.
The EPA expected to continue excluding most beneficial uses of
CCRs from hazardous waste regulation, however, noting that they
"offer significant environmental benefits." Id. at 35,154.
         In   April  2015,   EPA   settled   on  the  subtitle   D
classification for coal combustion waste, and it set national
minimum criteria for landfills receiving CCRs for disposal.
Hazardous and Solid Waste Management System; Disposal of Coal
Combustion Residuals from Electric Utilities ("2015 Rule"), 80
Fed. Reg. 21,302 (Apr. 17, 2015), 2015 WL 1734632.      Beneficial
uses remained excluded from regulation. Id. at 21,309.


                                    - 4 -
that    are   "environmentally          sound"       and       maximize    the     reuse    of

recoverable resources.             42 U.S.C. § 6941.                   To advance those

objectives, states and regional authorities are provided technical

and financial assistance to develop and implement solid waste

disposal      plans,      consistent         with    federal       guidelines,         to   be

submitted for EPA approval.              Id. §§ 6941, 6943, 6946-47.                     Among

other     requirements,        the      state        plans       must      "prohibit        the

establishment of new open dumps within the State," and require

that solid waste either be used for resource recovery, disposed of

in     sanitary     landfills,         "or     otherwise         disposed        of    in   an

environmentally        sound   manner."             Id.    §    6943(a)(2).           Congress

directed the EPA to adopt "regulations containing criteria for

determining       which    facilities        shall    be       classified     as      sanitary

landfills,"       and,    under    those       criteria,         "a     facility      may   be

classified as a sanitary landfill . . . only if there is no

reasonable     probability        of    adverse       effects         on   health      or   the

environment from disposal of solid waste at such facility."                                 Id.

§ 6944(a).

              The Commonwealth's plan to regulate the disposal of non-

hazardous solid waste at landfills, approved by the EPA in 1994,

gives the EQB "authority and responsibility for implementing and

enforcing solid waste management regulations, including a permit

program, inspection authority and enforcement activities."                                   59

Fed. Reg. 44,144, 44,145-46 (Aug. 26, 1994), 1994 WL 460341.                                The


                                         - 5 -
EPA notice approving Puerto Rico's program stated that the EQB had

adopted    comprehensive      regulations       governing    waste    disposal

"intended to bring Puerto Rico into full conformity" with federal

specifications, id. at 44,145, and that Puerto Rico's application

showed    compliance   with   "all   of   the    statutory   and     regulatory

requirements established by RCRA," id. at 44,146. The Commonwealth

was thus "granted a determination of adequacy for all portions of

its municipal solid waste permit program."           Id. 2

B. Commonwealth Law: Environmental Public Policy Act

            The Environmental Public Policy Act of 2004 designates

the EQB as the agency charged with managing Puerto Rico's response

to federal laws pertaining to "environmental conservation, natural

resources,    solid    waste,     and     other     matters"       related   to

environmental quality.        P.R. Laws Ann. tit. 12, § 8002g.            Among

other functions, the statute authorizes the EQB to (1) "adopt,

promulgate, amend and repeal rules and regulations for solid waste



     2  The EPA approval was for Puerto Rico's "municipal solid
waste permit program," 59 Fed. Reg. 44,144, and the regulation
establishing    minimum   national    criteria    likewise   refers
specifically to "municipal solid waste landfill (MSWLF) units," 40
C.F.R. § 258.1. Although the parties and district court refer to
the landfills at issue in this case as "sanitary" landfills, rather
than MSWLFs, the EQB's authorization for placement of CCRs is based
on the landfills' compliance with "the design and operation
criteria laid down in Title 40, Part 258 of the Code of Federal
Regulations under Subtitle D of the RCRA and [Puerto Rico
regulations]." EQB Resolution No. 14-27-20, Sept. 2, 2014, at 13.
Hence, our analysis presumes the sanitary landfills in this case
are equivalent to MSWLFs.


                                     - 6 -
disposal and establish the sites and methods to dispose of such

solid    waste,"    id.   §     8002c(b)(4)(A);          (2)    "adopt     rules   and

regulations to establish a permit-awarding and licensing mechanism

that regulates the control of the pollution in the air and water

and by solid waste and noise," id. § 8002c(b)(3)(E); and (3) issue

orders    "that,   in   its   judgment,   are      necessary       to    achieve    the

purposes of [the Act] and the regulations promulgated thereunder,"

id. § 8002c(a)(8).

              Under its statutory authority, the EQB adopted State

Regulation No. 5717, which consists of a series of rules governing

the management of non-hazardous solid waste.                   See P.R. Envtl. Laws

& Regs. No. 5717 ("the 1997 Regulation").                  The 1997 Regulation's

purposes      include   "[t]o    establish     a    program      for     the   design,

construction, operation, closure and post-closure maintenance of

[sanitary landfills] for non-hazardous solid waste."                       The Rules

specify, for example, where such facilities may be located (Rule

540), design criteria (Rule 541), the minimum personnel and their

training (Rules 543, 544), and the need for a system of ground

water protection and monitoring (Rules 551-558).

              A "final resolution or decision" of the EQB is reviewable

"in     the   manner    provided    for   in       the    Puerto        Rico   Uniform

Administrative Procedures Act," and EQB decisions may not be

"stayed, unless so ordered by the Circuit Court of Appeals of

Puerto Rico or by the Governing Board [of the EQB] itself."                        P.R.


                                     - 7 -
Laws Ann. tit. 12, § 8002c(a)(8); see also id. § 8002f(a)(4)

(providing that "[a]ny person adversely affected by a resolution,

order or decision of the Governing Board [of the EQB] may request

the latter to reconsider its determination or request a review by

the Court of Appeals of Puerto Rico").    Individuals who fail to

comply with EQB resolutions or orders "shall be guilty of a

misdemeanor," id. § 8002j(a), and may be subject to criminal or

administrative fines, damages, and sanctions, id. §§ 8002j(a)-(c).

C. Local Authority: Autonomous Municipalities Act

          Puerto Rico's Autonomous Municipalities Act gives local

governments authority to exercise their "legislative and executive

powers in any matter of a municipal nature" to promote "the welfare

of the community and its economic, social and cultural development"

and to protect "the health and safety of the people."    P.R. Laws

Ann. tit. 21, § 4051(o). A separate provision vests municipalities

with "the powers that are necessary and convenient to carry out"

some twenty-odd functions, id. § 4054, including to "[e]stablish

solid waste collection services and programs and public sanitation

programs in general, and adopt the standards and measures that are

necessary for the improvement and adequate control and disposal of

waste," id. § 4054(a).    This municipal authority is "subject to

applicable legislation," id. § 4051(o), and "subordinate[] to the

Constitution of the Commonwealth of Puerto Rico and to its laws,"

id. § 4003.   The required compatibility of local and commonwealth


                               - 8 -
law   also     is   recognized     in     a   provision   that   authorizes

municipalities      to   adopt   ordinances      regulating   "solid   waste

collection management," stating that such measures must be "in

harmony with the environmental public policy of the Commonwealth

of Puerto Rico."     Id. § 4055.

                                        II.

             We now sketch the background of the dispute before us,

drawing liberally from the district court's well-crafted summary.

The facts set forth here are undisputed.

A. Factual Background

             1. AES-PR and the Placement of CCRs

             AES-PR's coal-fired power plant, located in Guayama,

produces approximately fifteen percent of the electricity used in

Puerto Rico.     The Guayama facility imports the coal from Colombia

and, pursuant to a long-term contract, AES-PR sells the electricity

generated at the plant to the Puerto Rico Electric Power Authority

("PREPA").

             The combustion of coal produces two types of ash: bottom

ash and fly ash, which are collectively labeled coal combustion

residuals, and referred to as CCRs.           AES-PR produces approximately

200,000 to 250,000 tons of CCRs each year, some of which it uses

in a manufactured aggregate product marketed in Puerto Rico under




                                    - 9 -
the trade name AGREMAX ("Agremax"). 3           According to AES-PR, Agremax

has various beneficial uses, including as "structural fill" for

building     construction       and    as     "subbase    material       in   road

construction."      Agremax also has waste treatment applications; it

can be used to solidify liquid waste, 4 or be placed each day on

top of solid waste in a landfill -- a use known as "daily cover"

-- to prevent the waste materials from spreading.                In the latter

role, Agremax substitutes for soil and other natural materials.

See 40 C.F.R. § 258.21(a) (stating that sanitary landfills "must

cover disposed solid waste with six inches of earthen material at

the end of each operating day, or at more frequent intervals if

necessary,    to    control   disease       vectors,   fires,   odors,    blowing

litter, and scavenging"); id. § 258.21(b) (allowing the "Director

of an approved State" to approve "[a]lternative materials" for

daily cover).

           In September 2014, the EQB Board of Governors issued

Resolution    No.    14-27-20    ("the       2014   Resolution")     authorizing

disposal of CCRs generated by AES-PR's coal plant at sanitary

landfills approved by the EQB that meet the design and operation

requirements of RCRA's subtitle D and the Commonwealth's 1997



     3 Agremax is produced from a mixture of CCRs and water; the
mixture is compressed and allowed to cure, during which time it
hardens into what is generically called "rock ash."
     4 Federal law places a number of restrictions on the disposal
of liquid waste in sanitary landfills. See 40 C.F.R. § 258.28.


                                      - 10 -
Regulation.   Before a sanitary landfill may begin receiving CCRs

for disposal, however, it must file an application to modify its

operation permit and submit a plan that, at a minimum, includes

"adequate methods to control the material particles and compact

the waste; a description of the safety and protection equipment of

the operators and employees of the facility; a detailed description

of the runoff control system; and a description of the groundwater

monitoring plan."     The 2014 Resolution similarly limits the use of

CCRs as daily cover to approved sanitary landfills that meet the

specified requirements, and it likewise requires submission of an

application with an amended operation and emergency plan as a

prerequisite for such use.

           AES-PR   has     contracts    with    the   operators   of   three

landfills in Puerto Rico -- Peñuelas Valley Landfill and Ecosystems

Peñuelas   Landfill    in    Peñuelas,     and    El   Coquí   Landfill   in

Humacao -- to provide CCRs, including Agremax, for use as daily

cover, or to solidify non-hazardous liquid waste, or for disposal.

All three landfills are lined, sanitary landfill systems designed

to meet RCRA and EQB specifications.        They were issued permits by

the EQB to operate as facilities for the final disposal of non-

hazardous solid waste.

           In October 2015, the EQB Board issued Resolution No. 15-

23-1 ("the 2015 Resolution") approving requests by the El Coquí

and Peñuelas Valley landfills to receive CCRs generated by AES-


                                  - 11 -
PR.   Specifically, the EQB approved the use of Agremax to solidify

liquid waste in the Peñuelas Valley Landfill and reaffirmed its

prior authorization for the use of other CCRs at that landfill for

the   same   purpose.      The   EQB    also    approved   disposal    of   CCRs,

including Agremax, in both landfills.             The 2015 Resolution further

advised the landfills that, if they wished to use Agremax for daily

cover, they needed to apply for a waiver from the EQB by following

the procedures specified in the 1997 Regulation. 5                Several months

later, in January 2016, the EQB also authorized disposal of CCRs,

including Agremax, in the Ecosystems Peñuelas Landfill, and it

similarly directed Ecosystems to follow the procedures specified

by Puerto Rico law if it sought approval for using CCRs for daily

cover.       Ecosystems'    permit      did     not   authorize    liquid   waste

solidification with CCRs "because the necessary facilities for

these purposes have not been built."

             2.   The Humacao and Peñuelas Ordinances

             More than two years before the EQB issued its 2015

Resolution, the Municipality of Peñuelas adopted Ordinance Number

13 (the "Peñuelas Ordinance"), and several months later, the

Municipality of Humacao adopted Ordinance Number 21 (the "Humacao


      5The Resolution notes that the Humacao landfill's 2013
Operation Plan "listed the materials that the facility would
petition for in a future request for a waiver as materials proposed
as alternate cover."    Among the materials listed was "Rock Ash
from the AES generation plant." However, no request for a waiver
had been submitted at the time the Resolution was issued.


                                       - 12 -
Ordinance"), both of which prohibit the placement of CCRs on the

ground within the boundaries of their municipalities, including in

sanitary landfills. 6   Although the ordinances do not prohibit all

uses of CCRs, they bar the disposal and uses that the EQB has

authorized for the El Coquí, Peñuelas, and Ecosystems landfills

because those activities involve depositing CCRs on the ground. 7

          Both ordinances reflect particular concern about the

activities of AES-PR and its disposal of the coal ash produced by


     6 The Peñuelas ordinance provides, in pertinent part, that
"[t]he use of ashes coming from the burning of coal, in energy
generating plants, as landfill material and its depositing on lands
within the territorial limits of the Municipality of Peñuelas is
forbidden."

      The Humacao ordinance prohibits "[a]ny kind of use of the
ash derived from coal combustion in electric power generating
plants . . . as filler material, whether to level the terrain, for
landfills, or in any other kind of filler." Despite the Humacao
ordinance's focus on the use of CCRs as "filler material," the
municipality's administrator testified in his deposition that the
measure   prohibits   CCRs  from   being   deposited  within   the
geographical boundaries of Humacao.      In addition, defendants'
motion for summary judgment states that the ordinances ban "the
depositing of said CCRs on the ground within the geographical
limits of the Municipalities in question." Although the breadth
of the prohibition does not affect the outcome of this appeal, we
accept the defendants' characterization for purposes of our
analysis. Cf. AES Puerto Rico, L.P. v. Trujillo-Panisse, 199 F.
Supp. 3d 492, 512 (D.P.R. 2016) (noting that the ordinances "allow
CCRs to be bought, sold, and transported in the municipalities so
long as they are not deposited on the ground in the process").

     7 Indeed, appellees do not argue -- and did not argue below -
- that their ordinances do not apply to the specific uses of CCRs
authorized by the EQB in those landfills. Although appellees note
that the ordinances do not "pose a complete ban on the use of
CCRs," the uses contemplated by the EQB resolution -- disposal,
alternative daily cover, and waste solidification -- are not among


                               - 13 -
its coal-fired power plant.    In background explanatory clauses,

the ordinances discuss AES-PR's extensive use of coal ash in Puerto

Rico, making explicit reference to Agremax.     Both ordinances cite

studies revealing unsafe levels of toxic substances associated

with coal ash deposits and conclude that such deposits present a

threat to the environment and human health. 8

          In accordance with the EQB Resolution, AES-PR delivered

Agremax and CCRs in other forms to the landfills. 9   In April 2016,

the Municipality of Humacao responded by fining El Coquí Landfill

for the "[u]se of ash from burning coal."         On the same day,

Humacao's mayor sent the landfill a letter asking it to "refrain




those uses that appellees claim the ordinances permit. Nor did
appellees argue in their summary judgment briefing that the
ordinances' prohibition on "depositing of . . . CCRs on the ground"
excludes the three EQB-authorized uses of CCRs.

     8 The Humacao ordinance states that "[d]epositing such ash
represents a threat to the environment and the health of people
exposed thereto when it is blown by the wind or when it runs off
into surface and/or underground water."   The Peñuelas ordinance
similarly states:

          The deposit of ashes as landfill creates toxic
          substances situations blown by the wind and
          breathed by its inhabitants, which would
          entail the suffering of breathing ailments,
          possible birth defects and a high percentage
          in the pollution of surface and subterranean
          water due to the runoff of rain and leaching
          to the aquifers.

     9 Although AES-PR had previously been depositing CCRs in the
landfills in Humacao and Peñuelas, we focus in this case on its
activities following the EQB's 2015 Resolution.


                              - 14 -
from receiving coal combustion products or ash . . . regardless of

how such products are being used or under what name you are

receiving it," and stating that the municipality would be "forced

to reconsider" its contractual relationship with the facility if

the practice did not stop.       The maintenance manager of the AES-PR

plant reported in an affidavit that, also in April 2016, the

Municipality    of   Peñuelas    "used     municipal      trucks      and     other

municipal   equipment   to   physically        block    the    entrance     to    the

Peñuelas    Valley   Landfill    to    prevent    the    tanker      trucks      from

delivering AES-PR's CCRs to the Landfill for use to solidify liquid

wastes."

B. Procedural Background

            In its complaint against the municipalities of Peñuelas

and Humacao and their mayors, AES-PR asserted that the ordinances

restricting    the   placement    of    CCRs    violate       both   federal      and

Commonwealth law.    Among other contentions, AES-PR argued that the

local laws are preempted by both federal and Commonwealth law

because they prohibit activities involving CCRs that are permitted

by RCRA and explicitly authorized by the EQB. 10 The company alleged

that its "coal combustion products have repeatedly been tested and



     10AES-PR's complaint also alleges violations of the federal
Commerce Clause, the Due Process Clauses of the United States and
Puerto Rico constitutions, and the federal and Puerto Rico
Contracts Clauses.     The complaint further asserts that the
ordinances are void and ultra vires under Puerto Rico law.


                                  - 15 -
found safe for many applications, including as daily cover for

solid waste landfills, in construction as structural fill, and as

subbase material in road construction."     AES-PR's complaint sought

declaratory and injunctive relief, as well as damages.

            In May 2015, AES-PR moved for partial summary judgment

on its federal and state preemption claims.        The district court

denied the motion, rejecting both preemption theories. 11    The court

held that RCRA does not preempt the ordinances because the federal

law does not indicate a preference for "one type of beneficial use

(such as daily cover) over any other," and the defendants "have

not completely banned CCRs within their boundaries; they simply

have banned one of several possible methods of use or disposal."

AES Puerto Rico, L.P. v. Trujillo-Panisse, 133 F. Supp. 3d 409,

426 (D.P.R. 2015) ("AES-PR I").      With respect to Commonwealth law,

the court "decline[d] to strike down the Ordinances as out of

'harmony' with Commonwealth law, particularly because Commonwealth

law permits both the EQB and municipalities to regulate in this

arena."    Id. at 429.

            In March 2016, after the close of discovery, AES-PR again

moved for partial summary judgment.          The company renewed its

argument    that   the   municipal   ordinances   were   preempted   by




     11 The court also denied defendants' motion for judgment on
the pleadings, which raised issues of standing, ripeness, and
timeliness. That ruling is not before us.


                                - 16 -
Commonwealth law, relying in part on the EQB's 2015 Resolution

authorizing the use and disposal of CCRs at the El Coquí and

Peñuelas Valley landfills -- which the EQB had issued shortly after

the district court's prior ruling.            AES-PR also sought summary

judgment under the federal Commerce Clause because the ordinances

"discriminate   against     products    --   CCRs,   including   Agremax    --

derived from imported coal" and improperly burden interstate and

foreign commerce in excess of "any putative local benefits."               In

a cross-motion, the defendants sought summary judgment on AES-PR's

federal claims and dismissal of any remaining Commonwealth law

claims.

          In its second Opinion and Order, the district court

reaffirmed its previous denial of summary judgment for AES-PR on

the federal preemption claim and granted summary judgment for

defendants on that claim, noting that AES-PR had not alleged any

changes in federal law that would affect the court's analysis.

AES Puerto Rico, L.P. v. Trujillo-Panisse, 199 F. Supp. 3d 492,

506, 519 (D.P.R. 2016) ("AES-PR II"). 12                On the Commonwealth

preemption   claim,   the    court     reviewed   the    provisions   of   the

Autonomous Municipalities Act giving municipalities the general

authority to take actions to protect "the health and safety of the

people," P.R. Laws Ann. tit. 21, § 4051(o), as well as those


     12 As noted above, AES-PR had not renewed its request for
summary judgment based on federal preemption.


                                  - 17 -
specifically authorizing municipalities to adopt "measures that

are necessary for [the improvement] and adequate control and

disposal of waste," id. § 4054(a) (alteration in original). See

AES-PR II, 199 F. Supp. 3d at 506. The court recognized that

municipal ordinances must give way to Commonwealth law when there

is a conflict, but observed that "[a] municipal ordinance that

regulates in the same area as a Commonwealth law . . . will not be

preempted   'unless   it    is   impossible   to   harmonize    it    with   the

[Commonwealth]     law.'"    Id.   at   506-07     (second     alteration    in

original) (quoting Lopez v. Mun. de San Juan, 21 P.R. Offic. Trans.

71, 84 (1988)).

            The   court,    however,    declined   to   make    the   conflict

assessment concerning the Humacao and Peñuelas ordinances.                   It

noted that "[t]he Puerto Rico Supreme Court has not . . . resolved

whether resolutions of executive agencies carry the same power to

preempt as laws passed by the Puerto Rico Legislative Assembly,"

id. at 508, and it viewed that question under the Supremacy Clause

of the Commonwealth constitution as "a novel and complex issue of

state law," id. at 509. Comparing the issue to federal preemption,

the court observed that "the preemptive power" of federal agency

actions "depends on a myriad of factors and is a developing area

of jurisprudence."     Id. at 508 & n.14 (citing cases).             Describing

the Puerto Rico Uniform Administrative Procedures Act as similar

to the federal Administrative Procedures Act, the court concluded


                                   - 18 -
that the preemptive force of the EQB actions at issue in this case

is thus a question of Puerto Rico constitutional law "best resolved

by the Puerto Rico Supreme Court."          Id. at 508-09. 13     Accordingly,

the court declined to exercise jurisdiction over the Commonwealth

preemption claim. 14

           The    court    also   rejected     AES-PR's   claim    under   the

Commerce   Clause,        concluding   that     the   ordinances      do   not

discriminate facially or in effect against out-of-state products.

Id. at 512.      Although recognizing that the CCRS are derived from

imported coal, the court noted that "the Ordinances focus on CCRs,

which are produced domestically at the Guayama plant, not on the

imported coal used to create CCRs."           Id.   In any event, the court

observed, "[w]hether focusing on coal or CCRs, the burden of the




     13The court also noted that "several of the Commonwealth law
issues presented are already being litigated in related cases in
Commonwealth courts." AES-PR II, 199 F. Supp. 3d at 519. In one
of those actions, the Municipality of Peñuelas sued Ecosystems,
Inc. seeking to enjoin the use of Agremax in the construction of
the Ecosystems Peñuelas Landfill.   The resolution of that action
is discussed infra.    In another civil action that was later
withdrawn, the Municipality of Humacao sought "a permanent cease
and desist order against the deposit of ash" in the El Coquí
landfill.
     14 Although the court observed that "[d]istrict courts may
certify a question of state law to the state's supreme court when
the state issue is determinative and there is no controlling
precedent from the state court on the issue," it opted instead to
decline jurisdiction. 199 F. Supp. 3d at 509.



                                   - 19 -
Humacao and Peñuelas Ordinances on interstate commerce is either

nonexistent or slight."        Id. at 514. 15

              On   appeal,   AES-PR    challenges      the    district   court's

rulings on both the federal and Puerto Rico preemption claims, as

well as on the federal Commerce Clause claim.                The company asserts

that    the    ordinances    "conflict    with   and    frustrate     the   full

implementation of Congress's goals" in RCRA and likewise conflict

with the Commonwealth's environmental public policy as enacted

through EQB resolutions.       The company further argues that, even if

the Commonwealth preemption claim raises a novel or complex issue

of Puerto Rico law, the court should have certified the question

to the Puerto Rico Supreme Court rather than dismissing the claim.

AES-PR also seeks reversal of the district court's Commerce Clause

ruling.

                                      III.

              We review de novo the district court's resolution of the

parties' cross-motions for summary judgment, Troiano v. Aetna Life

Ins. Co., 844 F.3d 35, 41-42 (1st Cir. 2016), and we may affirm

based on any ground supported by the record, id. at 42.                  In this




       15
        The court went on to consider, and ruled in favor of
defendants, on AES-PR's federal Contract Clause and due process
claims.   199 F. Supp. 3d at 514-18.     As with the Commonwealth
preemption   claim,   it   declined   to   exercise   supplemental
jurisdiction over the remaining Commonwealth claims, "specifically
the Puerto Rico ultra vires, Contract Clause, and Due Process
Clause claims." Id. at 519.


                                      - 20 -
instance, we have an advantage over the district court because of

a decision issued by the Puerto Rico Supreme Court after the

district court's ruling.            See Autonomous Mun. of Peñuelas v.

Ecosystems,     Inc.,     No.   CC-2015-0325,      Dec.   19,     2016,   Certified

Translation ("Ecosystems").           As we shall explain, that recent

precedent      confirms    our    reading     of   Puerto        Rico's   statutory

framework      governing    solid    waste     management,        bolstering      our

conclusion that the Humacao and Peñuelas ordinances are preempted

under Commonwealth law to the extent they bar uses of CCRs that

have    been   specifically      approved     by   the    EQB.      Resolving     the

Commonwealth     preemption      claim   in    favor      of     AES-PR   makes   it

unnecessary for us to address AES-PR's other arguments on appeal,

and we thus limit our discussion to that claim. 16


       16
        We recognize that the district court declined to exercise
jurisdiction over the Commonwealth preemption claim, a judgment
that ordinarily is subject to review only for abuse of discretion.
See, e.g., Ramos-Echevarría v. Pichis, Inc., 659 F.3d 182, 191
(1st Cir. 2011). However, the court's decision to dismiss that
claim was premised on its view that the preemptive force of EQB
resolutions was an unresolved issue of law. To the extent there
was uncertainty, we believe it was eliminated by the recent
Ecosystems decision. Hence, the court's rationale is no longer
sustainable as a matter of law and, indeed, the court indicated
that, absent the ongoing Commonwealth proceedings and the legal
uncertainty, it would have exercised supplemental jurisdiction.
See AES-PR II, 199 F. Supp. 3d at 519 (noting that "the advanced
stage of the litigation and the costs of translating documents
into English weigh in favor of the Court exercising supplemental
jurisdiction").    We thus consider the Commonwealth preemption
issue de novo -- like any other legal question raised on appeal.
See Highmark Inc. v. Allcare Health Mgmt. Sys., Inc., 134 S. Ct.
1744, 1748 (2014) ("Traditionally, decisions on 'questions of law'
are 'reviewable de novo,' decisions on 'questions of fact' are


                                     - 21 -
 A. The Statutory Framework

           As    described     above,     Puerto    Rico   law     envisions     a

collaboration    between     Commonwealth     and    local   authorities       in

dealing with solid waste.         See, e.g., P.R. Laws Ann. tit. 21,

§ 4055.   However, in the case of a conflict, the statutory scheme

explicitly recognizes the preeminence of Commonwealth law.                     Id.

(stating that municipal measures concerning solid waste management

must be "in harmony with the environmental public policy of the

Commonwealth of Puerto Rico"); see also Liberty Cablevision of

P.R., Inc. v. Mun. of Caguas, 417 F.3d 216, 221-22 (1st Cir. 2005)

(noting that municipalities exercise only those powers derived

from the state, and, thus, "every municipal ordinance must be in

harmony   with   [state]     government    law,    which   shall    prevail     in

conflicting situations" (alteration in original) (quoting Lopez,

21 P.R. Offic. Trans. at 84)); see also P.R. Laws Ann. tit. 21,

§ 4003 (stating that "[t]he municipality is the juridical entity

of local government, subordinated to the Constitution of the

Commonwealth of Puerto Rico and to its laws"); id. § 4051(o)




'reviewable for clear error,' and decisions on 'matters of
discretion' are 'reviewable for "abuse of discretion."'" (quoting
Pierce v. Underwood, 487 U.S. 552, 558 (1988))); see also, e.g.,
Smith v. Holder, 627 F.3d 427, 433 (1st Cir. 2010) (concluding
that a decision "based on legal error" was an abuse of discretion).


                                   - 22 -
(stating      that    municipal       authority         is   "subject      to   applicable

[Commonwealth] legislation").

              The district court recognized this legislated hierarchy,

but it questioned whether EQB resolutions carry the force of law

such that an EQB permit allowing disposal of CCRs in a sanitary

landfill would necessarily supersede a local ordinance prohibiting

that disposal.         See AES-PR II, 199 F. Supp. 3d at 508 ("The Puerto

Rico Supreme Court has not . . . resolved whether resolutions of

executive agencies carry the same power to preempt as laws passed

by    the     Puerto       Rico     Legislative         Assembly.").            The       court

acknowledged,        however,       that    if    EQB    resolutions        and     landfill

permits authorized thereunder "carry the full force of law, then

the municipal Ordinances would likely be preempted to the extent

that they conflict."          Id.    As we have recounted, the district court

declined to delve into the legal force of the EQB authorizations

at issue in this case.            See id. at 509.

              Unlike the district court, we find that the governing

statutes      are    themselves      revealing      on       the    role   played     by    EQB

resolutions in establishing Commonwealth law.                              As an initial

matter,       the    EQB    is    given     the     overall         authority       for     the

Commonwealth's compliance with RCRA, see P.R. Laws Ann. tit. 12,

§    8002g,    and    it    has   express        authority         to   adopt   "rules      and

regulations for solid waste disposal" and "establish the sites and

methods to dispose of such solid waste," id. § 8002c(b)(4)(A).                              In


                                           - 23 -
other words, the Commonwealth's law on solid waste management is

made by the EQB.

          Moreover, the "final resolution[s] or decision[s]" of

the   EQB's    Governing   Board    are     treated   as   decisive   under

Commonwealth law, subject only to review by the courts.                 Id.

§ 8002c(a)(8).     By statute, EQB decisions may not be "stayed,

unless so ordered by the Circuit Court of Appeals of Puerto Rico

or by the [EQB Board] itself."         Id.; see also id. § 8002f(a)(4)

(providing that "[a]ny person adversely affected by a resolution,

order or decision of the Governing Board [of the EQB] may request

the latter to reconsider its determination or request a review by

the Court of Appeals of Puerto Rico").          As further evidence that

EQB decisions carry the full force of law -- including resolutions

such as the one authorizing use and disposal of CCRs at the

Peñuelas and Humacao landfills -- there are sanctions imposed for

failure to comply with the agency's rulings.          Individuals who fail

to comply with any EQB "resolution, order or agreement . . . shall

be guilty of a misdemeanor," and also may be subject to criminal

or administrative fines, damages, and sanctions.           Id. §§ 8002j(a)-

(c) (emphasis added).

          In     our    view,      these    provisions     (1)   assigning

responsibility to the EQB for Puerto Rico's policy on solid waste

disposal, (2) limiting any review of EQB decisions to judicial

actions, and (3) imposing criminal consequences for failure to


                                   - 24 -
comply    with    EQB    directives   definitively        establish       final   EQB

decisions on solid waste as Commonwealth law with preemptive power

over     local    ordinances.         These     provisions        are    explicitly

comprehensive in their scope, giving the force of law not only to

generally applicable rules and regulations, but also to "any

resolution,      order   or   agreement    dictated       by    the   Board."     Id.

§ 8002j(a).

            We are all the more persuaded of this view in light of

the Puerto Rico Supreme Court's recent Ecosystems decision, in

which    both    a   majority    opinion      and    concurrence        address   the

preemptive effect of EQB decisions on matters relating to the

handling of solid waste -- and, specifically, on the use of CCRs.

We thus turn to that decision.

B. The Ecosystems Opinion

            In the Ecosystems case, the Municipality of Peñuelas

sought to enjoin Ecosystems, Inc. from using Agremax as filler

material in the construction of its sanitary landfill. Ecosystems,

Inc. had been granted a construction permit by Puerto Rico's Office

of Permit Management and the EQB to build the facility, but the

permit did not specify the materials to be used in the project.

See Ecosystems Majority Op., at 2 ("Ecosystems Op.").                      Following

enactment of the Peñuelas ordinance banning the deposit of CCRs in

the municipality, Ecosystems, Inc. obtained an amended permit

"authorizing,        among    other   things,       the   use    of     manufactured


                                      - 25 -
aggregate as filling material in the construction."       Id. at 3.

The amended permit, however, did not reference or approve any

particular type of aggregate fill material.   Id.   The Municipality

thus maintained that it could bar the use of Agremax pursuant to

its ordinance because that prohibition did not conflict with the

EQB's generally worded authorization.     See Ecosystems Concurring

Op. at 8 ("Concurring Op.") (noting that manufactured aggregates

may be created from "rubble from demolition of buildings" and

"removed pavement," as well as from coal ash).

          In a lengthy analysis, the Puerto Rico Supreme Court

first took up the question of which entity is "in charge of

establishing in Puerto Rico the requirements applicable to the

handling and disposal of . . . solid waste," Ecosystems Op. at 8-

9, and it reviewed the missions of the three levels of government

that share responsibility for setting the environmental agenda in

the Commonwealth, id. at 9-20.      Noting that the EPA's 2015 Rule

established only "minimum national criteria to dispose of coal

combustion residuals," id. at 11-12 (emphasis omitted), the court

observed that "states may impose stricter requirements in relation

to this matter," id. at 12 (emphasis omitted); see also id. at 13

("[I]t is undeniable that a state may validly prohibit the disposal

and use of residuals from the burning of coal for energy production

within its territorial limits.").




                              - 26 -
          The court then considered the role of the EQB.    It noted

that the agency is authorized "[b]y express mandate" to "deal with

matters related to adequate disposal of solid waste," id. at 14

(citing P.R. Laws Ann., tit. 12, § 8002c), including by means of

"orders that it may deem necessary to make sure that the operation

of these plants or systems does not harm the environment," id. at

15.   After reviewing EQB regulations governing solid waste, the

court summed up: "In short, [EQB] is the agency in charge of

determining the form and manner in which to install, operate and

maintain facilities for the final disposal of solid waste, for

which it approves construction permits in accordance with its

public policy."   Id. at 17.

          Turning to the role of municipalities, the court noted

that the Commonwealth's public policy is to give municipalities

"as much autonomy as possible and provide them with the financial

tools and necessary powers and faculties to assume a central and

fundamental role in the urban, social and economic development of

our country."   Id. at 18.   These powers, the court stated, include

"provid[ing] by way of ordinance the way in which the handling of

solid waste shall be carried out."       Id. at 19 (citing P.R. Laws

Ann. tit. 21, § 4055) (emphasis omitted).    However, the court also

recognized that municipal power is subject to a higher authority,

and a municipality cannot "promote and further its own public

policy" if that policy conflicts with Commonwealth law.      See id.


                                - 27 -
at 20 (stating that a municipality may not act "in contravention

with the public policy established by the State" (citing López, 21

P.R. Offic. Trans. at 84)).

           The court then addressed the specific case before it,

observing that the amended EQB permit issued for the Ecosystems

landfill did not "expressly authorize[]" the use of CCRs in the

construction.      Id.    at   21.      Rather,    as   noted    above,   "the

authorization to fill with manufactured aggregate was issued in

the generic or broad definition of the term," Concurring Op. at 9,

meaning that it covered both Agremax and aggregate manufactured

from materials other than coal ash.           The court also pointed out

that the permit did not purport to override "local prohibitions."

Ecosystems Op., at 21.          In addition, the court observed that

neither the EPA nor the EQB had imposed rules governing the use of

CCRs as construction materials.          Id. at 22-23.     Hence, although

the EQB permit theoretically authorized the use of Agremax in the

landfill construction -- as one type of "manufactured aggregate"

-- neither the permit nor any other applicable law specifically

addressed or approved the use of Agremax in the construction

project.   The court thus identified no federal or Commonwealth law

in direct conflict with the Peñuelas ordinance.

      Accordingly,       the   court   concluded    that   the    ordinance's

prohibition of coal ash as fill material could be enforced against

Ecosystems, Inc.     Id. at 24.      That conclusion rested, however, on


                                     - 28 -
the   court's   determination    that   the   EQB   "at    present   has   not

preempted the field as to the use of aggregate manufactured from

ash produced while burning coal as construction material."             Id. at

23 (emphasis omitted).    Importantly, the court recognized that the

EQB could accomplish preemption: "Nothing prevents the [EQB] from,

in the future, exercising its regulatory power as to this matter

and expressly preempting the field."            Id.       Indeed, the court

reiterated near the conclusion of its opinion "that what is decided

herein by this Court does not prevent the [EQB] from establishing

public policy for the Commonwealth of Puerto Rico as to this

matter, if it deems appropriate and in accordance with the legally

provided mechanisms."     Id. at 29.    A concurring opinion emphasized

the same point:

                We clarify, as done in the Court Opinion,
           that the [EQB] may, as a matter of public
           policy of the State, regulate the use of
           aggregates including the ash produced when
           burning coal. The decision taken by the Board
           as to this matter shall necessarily prevail
           over municipal decisions.     Otherwise, this
           would lead to balkanization of the State.

Concurring Op. at 10 n.10.

           The two opinions leave no doubt that this preemptive

force    attaches    to    EQB    resolutions         addressing     specific

circumstances, as well as to the agency's more broadly based

regulations.    Both opinions focus on the EQB-approved construction

permit for the Peñuelas Valley landfill construction project.              The



                                  - 29 -
majority notes that, even as amended after the Peñuelas ordinance

was enacted, "the permit did not state anything as to the use of

this type of construction material [CCRs].                       That is, the material

prohibited      by     the    Municipal          Ordinance           was     not     expressly

authorized."         Ecosystems Op. at 21.               From this observation, we

think it a fair and obvious inference that, if the permit had

expressly authorized the use of CCRs, the municipal ordinance could

not have overruled the EQB.                Indeed, later in their opinion, the

majority confirmed that the ordinance's enforceability would be

precluded by conflicting EQB action, including in a permit, when

they     explained     that        the    ordinance        was       enforceable       against

Ecosystems, Inc. "as it does not in any way violate the current

public    policy      of     the     Commonwealth          of    Puerto       Rico    or     the

construction permit issued by the [EQB and Permit Office]."                                  Id.

at 24 (emphasis added).

              The concurring member of the court likewise treated the

EQB permit as authoritative, noting that the amended permit issued

to Ecosystems, Inc. "was approved by the appropriate agencies and

that -- for the moment -- it is in effect."                          Concurring Op. at 7;

see    also   id.    (observing          that   "it   is    a    well-known        rule    that

administrative        proceedings         are   assumed         to   be     correct    and    in

accordance     with    regulations").             And,      like      the    majority,       the

concurring justice saw room for the Peñuelas ordinance alongside

federal and Commonwealth law because the amended Ecosystems permit


                                           - 30 -
authorized the use of manufactured aggregate generically, id. at

9, and the municipal ordinance could properly supplement the permit

in the absence of "federal or state regulations related to the use

of ash as aggregate material for fill," id. at 7.                       Hence, she

observed, Ecosystems, Inc. could use any manufactured aggregate

"as long as it is not aggregate from ash produced by burning coal"

-- a ruling that "sought to harmonize the regulatory faculties of

the Municipality with the State's reasoning power, as mandated by

the Autonomous Municipality Act."            Id. at 9-10.

           In this case, the question is whether EQB resolutions

and permits that explicitly approve particular uses for CCRs

preempt contrary municipal ordinances.                 Based on the foregoing

discussion, we must conclude that they do.                    In contrast to the

broad, generic language of the construction permit at issue in the

Ecosystems case, the EQB's 2015 Resolution provides, inter alia,

that "[t]he use of rock ash [i.e., Agremax] is authorized as a

material for the solidification process at the Peñuelas [landfill]

in   addition   to    the   use   of   the    CCR,    which    has   been   already

authorized."     The Resolution also gives explicit permission "to

include the CCR and rock ash in the list of non-hazardous solid

waste that may be disposed of at the Peñuelas [landfill] and

Humacao [landfill]."        The Resolution further contemplates the use

of rock ash as alternative daily cover at the two landfills,

subject   to    the   EQB's   approval       of   a   petition    for   a   waiver.


                                       - 31 -
Ecosystems     Peñuelas       Landfill's         operating     permit      likewise

explicitly identifies CCRs among the types of non-hazardous solid

waste "to be received for disposal" at the facility.                Appellees do

not contend that the terms "CCR" or "rock ash," as used in the EQB

resolutions here, are generic in the same way that the term

"manufactured aggregate" was held to be in Ecosystems.                      Nor do

they   counter      AES's     argument        that     Ecosystems   conclusively

established    that    EQB   resolutions         can   have   preemptive    effect.

Hence, in the words of the Ecosystems concurrence, "[t]he decision

taken by the [EQB] as to this matter shall necessarily prevail

over municipal decisions."          Id. at 10 n.10.

                                         IV.

             In sum, the EQB's authorization for particular uses and

disposal of CCRs in the Humacao landfill and the two Peñuelas

landfills preempts the bar on any such uses and disposal imposed

by the challenged municipal ordinances.                 According to the record

before us, the EQB has authorized (1) disposal of CCRs at all three

landfills,    and   (2)     the   use    of    CCRs,   including    Agremax,    for

solidification at the Peñuelas Valley Landfill.                 Further, the EQB

has invited requests for waivers to allow the use of Agremax as

alternative daily cover at the three landfills.

          Thus,       to   the    extent      AES-PR   has    complied   with   all

regulatory prerequisites for the deposit of CCRs at the three

landfills and obtained the EQB's approval to move forward, it is


                                        - 32 -
entitled to do so.   Accordingly, we vacate the summary judgment in

favor of the defendants, and remand the case to the district court

with directions that it enter judgment for AES-PR consistent with

this decision.   Each party shall bear its own costs.

          So ordered.




                               - 33 -
