 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued March 5, 2018                   Decided July 20, 2018

                        No. 17-5123

          ASSOCIATION OF AMERICAN RAILROADS,
                       APPELLEE

                             v.

 UNITED STATES DEPARTMENT OF TRANSPORTATION, ET AL.,
                    APPELLANTS


        Appeal from the United States District Court
                for the District of Columbia
                    (No. 1:11-cv-01499)


     Patrick G. Nemeroff, Attorney, U.S. Department of
Justice, argued the cause for appellants. With him on the
briefs were Chad A. Readler, Acting Assistant Attorney
General, Jessie K. Liu, U.S. Attorney, Mark B. Stern, Michael
S. Raab, and Daniel Tenny, Attorneys, Steven G. Bradbury,
General Counsel, U.S. Department of Transportation, James
Owens, then-Acting General Counsel, Paul M. Geier, Assistant
General Counsel, Christopher S. Perry, Acting Deputy
Assistant General Counsel for Litigation and Enforcement, Joy
K. Park, Senior Trial Attorney, Juan D. Reyes III, Chief
Counsel, Federal Railroad Administration, and Zeb G. Schorr,
Assistant Chief Counsel.
                               2
    Thomas H. Dupree Jr. argued the cause for appellee.
With him on the brief were David A. Schnitzer, Kathryn
Kirmayer, and Daniel Saphire.

    Before: GARLAND, Chief Judge, and TATEL and MILLETT,
Circuit Judges.

    Opinion for the Court filed by Circuit Judge MILLETT.

    Dissenting opinion filed by Circuit Judge TATEL.

     MILLETT, Circuit Judge: A dispute between passenger
and freight trains over priority access to railroad tracks has
turned into a legal donnybrook over the bounds of
congressional power.        This court previously held that
Congress went off the constitutional rails by empowering
Amtrak to establish metrics and standards affecting track usage
over the opposition of the private freight railroads that own
those tracks and without the intermediation and control of a
neutral governmental decisionmaker. More specifically, this
court ruled that the Due Process Clause does not allow Amtrak
to use an arbitration process to impose its preferred metrics and
standards on its competitors, notwithstanding their opposition
and that of the Federal Railroad Administration.

     The question in this case is how to remedy that
constitutional problem. We hold that severing the arbitration
provision is the proper remedy. Without an arbitrator’s stamp
of approval, Amtrak cannot unilaterally impose its metrics and
standards on objecting freight railroads. No rule will go into
effect without the approval and permission of a neutral federal
agency. That brings the process of formulating metrics and
standards back into the constitutional fold.
                                3
                                I

                               A

     The Rail Passenger Service Act of 1970, Pub. L. No. 91-
518, 84 Stat. 1327, established Amtrak (a/k/a the National
Passenger Railroad Corporation) to “reinvigorate a national
passenger rail system that had * * * grown moribund and
unprofitable,” Association of American R.R. v. Department of
Transp., 721 F.3d 666, 668 (D.C. Cir. 2013) (American
Railroads I), and “to fully develop the potential of modern rail
service in meeting the Nation’s intercity passenger
transportation requirements,” Rail Passenger Service Act
§ 301, 84 Stat. at 1330. In passing that legislation, “Congress
recognized that Amtrak, of necessity, must rely for most of its
operations on track systems owned by the [regional] freight
railroads.” Department of Transp. v. Association of American
R.R. (American Railroads II), 135 S. Ct. 1225, 1229 (2015).

      Three years later, Congress granted Amtrak’s passenger
rail service “preference over freight transportation in using a
rail line[.]” 49 U.S.C. § 24308(c). To implement that priority
system, Congress authorized Amtrak to enter into agreements
with rail carriers and regional transportation authorities “to use
[the] facilities of, and have services provided by, the carrier or
authority under terms on which the parties agree.” Id.
§ 24308(a). Congress added that the “terms shall include a
penalty for untimely performance” by either party. Id. If
Amtrak and the carrier or authority could not agree on
governing terms, Congress empowered the federal Surface
Transportation Board to “order that the facilities be made
available and the services provided to Amtrak,” and to
                                4
“prescribe reasonable terms and compensation for using the
facilities and providing the services.” Id.1

     In 2008, Congress enacted the Passenger Rail Investment
and Improvement Act (“2008 Rail Act”), Pub. L. No. 110-432,
122 Stat. 4848, codified at 49 U.S.C. § 24101 note. That
statute reconfigured the process for Amtrak to coordinate its
rail access with private freight railroads. As is most relevant
here, the Act directed that Amtrak and the Department of
Transportation’s Federal Railroad Administration “shall jointly
* * * develop new or [shall] improve existing metrics and
minimum standards for measuring the performance and service
quality of intercity passenger train operations, including cost
recovery, on-time performance and minutes of delay, ridership,
on-board services, stations, facilities, equipment, and other
services.” Id. § 207(a). As part of that process, the 2008 Rail
Act requires Amtrak and the Administration to “consult[] with”
the Surface Transportation Board, rail carriers over whose rail
lines Amtrak trains operate, States, passenger representatives,
and Amtrak employees about the appropriate metrics and
standards. Id.

    If Amtrak and the Administration are unable to develop
those metrics and standards within 180 days, Congress
authorized “any party involved in the development of those
standards” to “petition the Surface Transportation Board to
appoint an arbitrator to assist the parties in resolving their
disputes through binding arbitration.”        2008 Rail Act
§ 207(d), 49 U.S.C. § 24101 note.

1
  Originally, the 1973 Act charged the Interstate Commerce
Commission with resolving any disagreement. 45 U.S.C. §§ 561,
562 (1970 ed.). That authority was transferred to the Surface
Transportation Board in 1996. American Railroads II, 135 S. Ct. at
1229; ICC Termination Act of 1995, Pub. L. No. 104-88, 109 Stat.
803.
                                5
                                B

                                1

     In tracing the history of this litigation, we write on a full
slate. In March 2009, Amtrak and the Federal Railroad
Administration published a Federal Register notice inviting
comments on proposed metrics and standards pertaining to
Amtrak’s invocation of its right under the 2008 Rail Act to
priority access to the railways. The Association of American
Railroads (“Railroad Association”) is a group of large freight
railroad owners that operate tracks that Amtrak uses. The
Railroad Association and its members submitted numerous
comments, mostly concerning the increased expense associated
with expanding and maintaining the needed track capacity and
the timing metrics. See, e.g., J.A. 165, 171, 176.

     The final metrics and standards that issued in May 2010
did not alleviate the Railroad Association’s concerns. So the
Railroad Association filed suit in federal district court
challenging the facial constitutionality of Section 207’s scheme
for promulgating metrics and standards. The Railroad
Association argued that the provision unconstitutionally
delegated regulatory power over private entities to Amtrak, an
allegedly non-governmental entity, by allowing it to influence
or control the content of the metrics and standards imposed on
its competitors. American Railroads Mot. for Summ. J.,
Association of American R.R. v. Department of Transp., Civ.
No. 11-1499 (D.D.C. May 31, 2012), ECF No. 8 at 7. The
district court found no constitutional problem and granted
summary judgment for the government. Association of
American R.R. v. Department of Transp., Civ. No. 11-1499
(D.D.C. May 31, 2012), ECF No. 17 at 2.
                                6
     On appeal, this court deemed Amtrak to be a private entity
and ruled that Section 207 unconstitutionally delegated
authority to a private party “to jointly develop performance
measures to enhance enforcement of the statutory priority
Amtrak’s passenger rail service has over other [private freight]
trains.” American Railroads I, 721 F.3d at 668.

     The Supreme Court vacated that constitutional ruling.
American Railroads II, 135 S. Ct. at 1234. The Court
emphasized that “Amtrak was created by the Government, is
controlled by the Government, and operates for the
Government’s benefit.” Id. at 1232. Consequently, when
undertaking “its joint issuance of the metrics and standards
with the [Federal Railroad Administration], Amtrak acted as a
governmental entity for the purposes of the Constitution’s
separation of powers provisions.” Id. at 1232–1233. The
Supreme Court then remanded the case for this court to address
whether Section 207 ran afoul of the Fifth Amendment’s Due
Process Clause by giving Amtrak, a “for-profit corporation[,]
regulatory authority over its own industry,” and whether the
arbitration provision violated the Appointments Clause, U.S.
CONST., ART. II, § 2, CL. 2. American Railroads II, 135 S. Ct.
at 1234.

                                2

    On remand, this court again held Section 207
unconstitutional. Association of American R.R. v. Department
of Transp. (American Railroads III), 821 F.3d 19 (D.C. Cir.
2016). We held that Section 207 unconstitutionally delegated
to Amtrak, a “self-interested entity,” id. at 31, the authority to
“regulate its resource competitors,” id. at 23, in violation of the
Due Process Clause.
                              7
     This court rejected the government’s argument that the
Federal Railroad Administration’s joint role in promulgating
the metrics and standards tempered any due process concerns.
We explained that the Administration “is powerless to overrule
Amtrak” because, if there is “intractable disagreement between
the two, the matter is resolved by an arbitrator, who may
ultimately choose to side with Amtrak” in binding arbitration.
American Railroads III, 821 F.3d at 35. Because the
arbitration provision prevents the Administration from
“keep[ing] Amtrak’s naked self-interest in check,” we
concluded, “the requirement of joint development does not
somehow sanitize the Act.”            Id.; see id. at 34. n.4
(distinguishing Supreme Court precedent upholding joint
regulatory efforts by “a self-interested group and a government
agency” because the Administration’s “authority to hold the
line against overreaching by Amtrak is undermined by the
power of the arbitrator” to independently authorize Amtrak’s
metrics and standards).

     Lastly, this court held that appointment of the arbitrator
violated the Constitution’s Appointments Clause. This court
concluded that the arbitrator’s binding decision constituted
final agency action. Yet the arbitrator was not appointed by
the President, but rather by an independent agency, the Surface
Transportation Board, which also had no oversight or review
of the arbitrator’s decision. American Railroads III, 821 F.3d
at 38–39.

                              3

    The case then returned to district court to remedy the
constitutional violations. With the agreement of both the
Railroad Association and the government, the district court
vacated the May 2010 metrics and standards. Association of
American R.R. v. Department of Transp., Civ. No. 11-1499
                               8
(D.D.C. Mar. 23, 2017), ECF No. 27 at 6. The district court
then declared Section 207’s entire Amtrak-influenced process
for formulating metrics and standards unconstitutional,
rejecting the government’s argument that severing Section
207(d)’s arbitration provision by itself would cure the
identified constitutional infirmities. Id. at 5.

                               II

     The district court had jurisdiction over this case under 28
U.S.C. § 1331, and we have jurisdiction to review its final order
under 28 U.S.C. § 1291. We review de novo questions
concerning the remediation of a statute’s unconstitutionality
and questions of statutory construction. See Stop This Insanity
Inc. Employee Leadership Fund v. FEC, 761 F.3d 10, 13 (D.C.
Cir. 2014).

                               A

                               1

     Now at round four of this appellate litigation, we reach the
question of how to remediate the constitutional violations
previously found. The government does not challenge the
prior panel’s constitutional holdings on this appeal and, in any
event, we are bound by them. The district court vacated the
most immediate byproduct of the constitutional violations—
the metrics and standards adopted in May 2010—and that
aspect of the district court’s decision is final and is also not
challenged on appeal. The question instead is how to
constitutionally right the statutory ship going forward.
Because the linchpin for Amtrak’s ability to unconstitutionally
exercise regulatory authority over its competitors was the 2008
Rail Act’s binding arbitration provision, severing Section
                               9
207(d) will fully cure the constitutional violations found in
American Railroads III.

     Declaring unconstitutional an Act of Congress, duly
adopted by the Legislative Branch and signed into law by the
Executive, is one of the gravest powers courts exercise.
Longstanding principles of constitutional avoidance caution
courts against exercising that power unless it is strictly
necessary to resolve a case. See, e.g., Ashwander v. Tennessee
Valley Auth., 297 U.S. 288, 347 (1936) (Brandeis, J.,
concurring); Syracuse Peace Council v. FCC, 867 F.2d 654,
657 (D.C. Cir. 1989). And even when a constitutional
question must be joined, courts must choose the narrowest
constitutional path to decision. Plaut v. Spendthrift Farm,
Inc., 514 U.S. 211, 217 (1995).

    When a statute has been held to be unconstitutional, an
important corollary to those principles of constitutional
avoidance is that the remedy should be no more severe than
necessary to cure the disease. When possible, courts must
preserve as much of a statute as is constitutionally possible,
because “[t]he cardinal principle of statutory construction is to
save and not to destroy.” Tilton v. Richardson, 403 U.S. 672,
684 (1971) (quoting NLRB v. Jones & Laughlin Steel Corp.,
301 U.S. 1, 30 (1937)).

     Our decision in American Railroads III points us down
that same narrow path. In concluding that the 2008 Rail Act’s
process for developing metrics and standards was
unconstitutional, this court’s analysis comprised two distinct
determinations: (1) that Amtrak was economically self-
interested in and competing with the freight railroads as to the
content of the metrics and standards, and (2) the 2008 Rail Act
endowed Amtrak with the power to regulate those competitors.
American Railroads III, 821 F.3d at 31. Both prongs were
                              10
required to make out a Due Process Clause violation. Id. at
31.

     This court’s resolution of that second prong identifies the
arbitration provision as the critical constitutional fissure.
After all, the constitutional problem in this case was not that
Amtrak exercised some role in formulating those metrics and
standards—Amtrak had some role under the 1970 Act and the
1973 amendment, which the freight railroads have not
challenged. Plus Amtrak’s participation to some extent is
inherent in the development of contracts between Amtrak and
individual freight railroads that embody those metrics and
standards. See 49 U.S.C. § 24308(a).

     Nor, as our prior opinion explained, would the
Constitution prohibit Amtrak from exercising some measure of
joint control with a disinterested governmental agency, as long
as that agency’s duty to protect the “public good” could check
Amtrak’s self-interest and prevent unfair harm to its
competitors. American Railroads III, 821 F.3d at 29.
Indeed, our prior opinion specifically noted that a number of
arrangements by which regulatory measures were imposed
through the “joint action of a self-interested group and a
government agency” had passed constitutional muster. Id. at
34 n.4 (citing Currin v. Wallace, 306 U.S. 1 (1939); Sunshine
Anthracite Coal Co. v. Adkins, 310 U.S. 381 (1940)).

     Instead, the straw that broke the camel’s back was that the
2008 Rail Act stripped the Federal Railroad Administration of
that independent ability to temper or prevent Amtrak from
adopting measures that promoted its own self-interest at the
expense of its freight railroad competitors. It was Section
207(d)’s binding-arbitration provision that both gave Amtrak
that independent regulatory muscle and disarmed the
Administration. The 2008 Rail Act charged Amtrak and the
                               11
Administration, at the outset, with developing the metrics and
standards jointly. 2008 Rail Act § 207(a), 49 U.S.C. § 24101
note. But critically, if that collaborative process stalled,
Section 207(d) allowed Amtrak on its own to request the
appointment of a Surface Transportation Board arbitrator.
2008 Rail Act § 207(d), 49 U.S.C. § 24101 note. The
arbitrator then had the authority, through binding arbitration, to
force the promulgation of final metrics and standards
regardless of the Administration’s, the private freight
railroads’, or anyone else’s objections to their terms.
American Railroads III, 821 F.3d at 39.

     So the arbitration provision is what constitutionally
derailed the statutory scheme. For it empowered Amtrak to
impose on its competitors rules formulated with its own self-
interest in mind, without the controlling intermediation of a
neutral federal agency. All Amtrak had to do was persuade
the arbitrator to rule in its favor. Once that happened, the
disinterested governmental agency—the Administration—
“[wa]s powerless to overrule Amtrak.” American Railroads
III, 821 F.3d at 35.         Whatever “equal authority” the
Administration initially had with Amtrak by virtue of the
charge to jointly develop the metrics and standards, that power
would evaporate “[w]hen there is intractable disagreement
between the two[.]” Id. At that point, “the matter is resolved
by an arbitrator, who may ultimately choose to side with
Amtrak.” Id. The Administration “cannot keep Amtrak’s
naked self-interest in check, and therefore the requirement of
joint development does not somehow sanitize the [2008 Rail]
Act.” Id.

     Emphasizing the centrality of the arbitration provision to
our constitutional decision, this court pointed to Amtrak’s
arbitration escape hatch to distinguish Supreme Court
precedent otherwise upholding programs for the joint private
                               12
and governmental promulgation of regulations. For example,
in Currin v. Wallace, the Tobacco Inspection Act of 1935,
7 U.S.C. §§ 511 et seq., delegated to the Secretary of
Agriculture the authority to set standards for various classes of
tobacco that would affect the commodity’s market pricing.
306 U.S. at 5–6. But the Secretary’s proposed standards and
prices would govern only if two-thirds of the tobacco growers
within the market region approved them by referendum. Id. at
15. The Supreme Court upheld that provision because the
Secretary’s ultimate control over the content of the standards
and prices submitted for approval meant that self-interested
producers had neither the power to craft the rules in their own
image nor to “force [them] upon a minority” of competitors.
Id.; see United States v. Rock Royal Co-operative, Inc., 307
U.S. 533, 577–578 (1939) (upholding marketing orders for
milk because, even though they were approved by two-thirds
of milk producers, the Secretary of Agriculture exercised
ultimate control over the prices set).

     Similarly, in Sunshine Anthracite Coal Co. v. Adkins, 310
U.S. 381 (1940), the Supreme Court upheld a provision in the
1937 Bituminous Coal Act, 15 U.S.C. §§ 828 et seq., under
which participating coal producers could propose minimum
coal prices to a government agency—the National Bituminous
Coal Commission. The Coal Commission, however, retained
complete authority to “approve[], disapprove[], or modif[y]”
the prices ultimately adopted. Id. at 388; see id. at 399.
Because the Commission exercised “authority and
surveillance” over the participating coal producers, and
because law-making remained in the hands of the agency and
was “not entrusted to the industry,” the Supreme Court
declared the statutory scheme to be “unquestionably valid.”
Id. at 399.
                               13
     The arbitration provision in the 2008 Rail Act broke from
that mold. Ultimate control over the regulatory standards did
not rest with a neutral governmental agency; it could be
exercised by Amtrak with an assist from the arbitrator.
American Railroads III, 821 F.3d at 34 n.4. “[T]he [Federal
Railroad Administration’s] authority to hold the line against
overreaching by Amtrak,” we explained, “is undermined by the
power of the arbitrator.” Id.

     Said another way, without the ability to resort to binding
arbitration, Amtrak would have no power to impose its own
self-interested regulatory measures on its competitors. While
Amtrak could press its views with the Federal Railroad
Administration, unless the Administration independently
determined that those standards were in the public interest—
not just Amtrak’s interests—Amtrak’s proposals would hit a
dead-end. See American Railroads I, 721 F.3d at 674 (stating
that, if the regulatory authority to set metrics and standards is
wielded by a governmental agency, “[Section] 207 is of no
constitutional moment”).

                               2

     Our dissenting colleague reads our prior decision
differently, concluding that American Railroads III
constitutionally quarantined Amtrak away from any
“participation” in the regulatory process “at all,” Dissent Op.
at 1, 7, and forbade even efforts to “convinc[e]” or “persuade”
the Federal Railroad Administration what the metrics and
standards governing its own performance should be, id. at 7,
13.

    But our prior opinion never said that the Constitution
required sidelining Amtrak throughout the regulatory process.
We were quite explicit about what the constitutional Due
                               14
Process problem was: Notwithstanding its self-interest, the
2008 Rail Act empowered Amtrak “to regulate” its competitors
and “to make law.” 821 F.3d at 23; see id. at 27 (“Our view
of the case can be reduced to a neat syllogism,” which turns at
each line of the syllogism on whether the Act gives Amtrak
“regulatory authority”); id. (due process question turns on
whether Amtrak has “rulemaking authority”); see also
American Railroads II, 135 S. Ct. at 1234 (remanding for
decision as to whether Amtrak unconstitutionally exercised
“regulatory authority” over its competitors).

      So the critical constitutional question is what in the 2008
Rail Act made Amtrak itself a regulator—that is, what allowed
it to make law. It was not, we said, Amtrak’s ability to engage
in “joint [regulatory] action” with the Administration. Such
joint efforts between “a self-interested group and a government
agency,” we specifically noted, raised no constitutional
eyebrow as long as the government agency could “hold the
line” against the entity’s “overreaching” to advance its own
self-interests. 821 F.3d at 34 n.4. The opinion then went on
to explain that the critical check on private interests that had
been present in those Supreme Court cases was missing here
precisely because the “[Administration] is powerless to
overrule Amtrak,” and when there is “intractable disagreement
between the two, the matter is resolved by an arbitrator, who
may ultimately side with Amtrak.” Id. at 35. As a result, the
Administration “cannot keep Amtrak’s naked self-interest in
check.” Id.

     The dissenting opinion rightly notes our holding that the
metrics and standards the Administration and Amtrak jointly
develop are forms of regulation, 821 F.3d at 33-34, and reads
our opinion as holding that the constitutional flaw was in
vesting “‘Amtrak [with] the authority to develop [those]
metrics and standards—constrained very partially . . . by the
                                15
[Administration] and the arbitrator[.]’” Dissent Op. at 8
(quoting 821 F.3d at 33). To the dissenting opinion, the
ensuing discussion about joint rulemaking efforts and the
Administration’s and arbitrator’s inability to rein Amtrak in
was simply an explanatory aside just answering the
government’s argument about precedent. Dissent Op. at 11-
12.

    Our opinion said otherwise, explicitly wrapping the two
points together. The source of the constitutional trouble, we
explained, was that the 2008 Rail Act vested “Amtrak [with]
the authority to develop [those] metrics and standards—
constrained very partially, as discussed below, by the
[Administration] and the arbitrator[.]” Id. at 33 (bold added).
The referenced “discuss[ion] below” was precisely the analysis
on the following pages of how the arbitration option allowed
Amtrak to escape the type of check on its self-interest that the
Due Process Clause requires when regulations are jointly
developed between a government agency and self-interested
groups. The two portions of the opinion cannot be delinked.

     The crux of the constitutional problem, in short, was not
that Amtrak had input or the opportunity to “persuade” the
Administration. Dissent Op. at 13. That happens all the time
in the regulatory process by all manner of self-interested
parties. “[P]articipation” is not regulation. Id. at 1. What
went wrong in the 2008 Rail Act was that Amtrak, through
unilateral resort to the arbitrator, had the power “to make law,”
821 F.3d at 23, by formulating regulatory metrics and standards
without the agreement or control of the Administration.2

2
  The dissenting opinion objects that the arbitration provision had
not even been invoked with respect to the May 2010 metrics and
standards that the freight railroads challenged. Dissent Op. at 9.
                                16

      The dissenting opinion also objects that the Federal
Railroad Administration itself is neither “disinterested” nor
tasked with promoting the freight operators’ interests.
Dissent Op. at 13. Our prior decision never suggested that the
Administration does not act in good faith to protect the public
interest, just like the other agencies involved in joint regulatory
development with private interests. To the contrary, it
explicitly noted that if Congress had “directed the [Federal
Railroad Administration] to develop [the metrics and
standards] alone,” Congress would have been giving regulatory
power to a “presumptively disinterested” government entity.
American Railroads III, 821 F.3d at 35 (quoting Carter Coal,
298 U.S. at 311). Anyhow, the relevant constitutional
question, as our prior opinion explained, is whether the
Administration can “check” Amtrak’s self-interests, 821 F.3d
at 35, not whether it can speak for a different self-interested
group.       With the arbitrator provision removed, the
Administration can stop a self-serving Amtrak proposal dead
in its tracks.

    Finally, the dissenting opinion notes that the
Administration is housed “in the same branch” of an Executive
agency as Amtrak. Dissent Op. at 13. But that is just a
reminder that, when it comes to formulating these metrics and
standards, the Supreme Court has held that “Amtrak act[s] as a
governmental entity,” 135 S Ct. at 1233, and thus is not purely
animated by self-interest.        That Amtrak has “public
objectives” to serve, id. at 1232, is yet another reason that the


That is beside the point because the Railroad Association leveled a
facial challenge to the 2008 Rail Act provisions. J.A. 20–21. That
facial challenge is why we also decided the Railroad Association’s
Appointments Clause challenge to the same never-appointed
arbitrator.
                               17
constitutional remedy does not require completely walling
Amtrak off from any role at all in the regulatory process.

                           *****

     Given all of that, eliminating the arbitration provision is
the key to curing the constitutional problem because it
eliminates Amtrak’s ability and power to exercise regulatory
authority over its competitors. Without the Administration’s
approval, Amtrak’s regulatory proposals would amount to
nothing more than trying to clap with one hand. Such an
ineffective endeavor would not offend the Due Process Clause.

                               B

     As a matter of constitutional law, excising Section
207(d)’s binding-arbitration provision would deprive Amtrak
of its unlawful ability to engage in regulatory self-help. But a
court may order such curative severance only if, as a matter of
statutory construction, doing so would leave a functioning
statutory scheme and would comport with congressional
objectives. See United States v. Booker¸ 543 U.S. 220, 258–
259 (quotations omitted); see also Bismullah v. Gates, 551 F.3d
1068, 1071 (D.C. Cir. 2009) (“[W]e must retain those portions
of the Act that are (1) constitutionally valid, (2) capable of
functioning independently, and (3) consistent with Congress’
basic objectives in enacting the statute.”) (quotations omitted).

   We hold that severing Section 207(d) is the proper
medicine in this case, for four reasons.

     First, there is a presumption in favor of severability. See,
e.g., United States v. National Treasury Employees Union, 513
U.S. 454, 488 (1995); Bismullah, 551 F.3d at 1071; Alaska
Airlines, Inc. v. Donovan, 766 F.2d 1550, 1560 (D.C. Cir.
                               18
1985). The “normal rule is that partial, rather than facial,
invalidation is the required course.” Free Enterprise Fund v.
Public Co. Accounting Oversight Bd., 561 U.S. 477, 508
(2010) (internal quotation marks omitted).

    That presumption enforces judicial restraint in
constitutional adjudication by ensuring that, to the extent
possible, courts “limit the solution to the problem, severing any
problematic portions while leaving the remainder intact.”
Free Enterprise Fund, 561 U.S. at 508 (internal quotation
marks omitted). After all, “the unconstitutionality of a part of
an Act” says nothing about “the validity of its remaining
provisions[.]” Id. (internal quotation marks omitted).

     To be sure, this question of statutory (re)construction
would be easier if the 2008 Rail Act contained a severability
clause. But it does not. Still, sometimes such congressional
“silence is just that—silence[.]” New York v. United States,
505 U.S. 144, 186 (1992) (internal quotation marks omitted).
The absence of a severability clause cuts neither against nor in
favor of severance; the presumption of severability remains
intact. Id.; see City of New Haven v. United States, 809 F.2d
900, 905 n.15 (D.C. Cir. 1987).

     Second, as to the requirement that the statute be functional
in the absence of the severed provision, the parallels between
the trimmed down 2008 Rail Act and the original 1970 and
1973 schemes offer substantial assurance that the statutory
scheme could function even with Section 207(d) pruned away.
To be sure, negotiations over what metrics and standards to
adopt may be harder without the binding-arbitration tiebreaker.
But the Federal Railroad Administration and Amtrak have been
working together on such matters for almost half a century, and
most of that time without the possibility of resort to binding
arbitration. We also assume that the Federal Railroad
                              19
Administration and Amtrak, which wears a governmental hat
in this role, American Railroads II, 135 S. Ct. at 1233, will
endeavor to promulgate the required rules in good faith and
consistently with their legislatively assigned duties, see CTIA-
The Wireless Ass’n v. FCC, 530 F.3d 984, 989 (D.C. Cir. 2008)
(agencies are presumed to exercise their duties in good faith).

     Third, narrowly severing Section 207(d) would better
comport with Congress’s objectives than would throwing the
entire Section 207 baby out with the bath water. In this regard,
we do not inquire what Congress intended, since it undoubtedly
intended the legislation as enacted. “The relevant question
* * * is not whether the legislature would prefer (A+B) to B,
because by reason of the invalidation of A that choice is no
longer available.” Leavitt v. Jane L., 518 U.S. 137, 143
(1996). Instead, we ask the more practical question of
“whether the legislature would prefer not to have B if it could
not have A as well.” Id.

     Severing Section 207(d) leaves intact Congress’s objective
of streamlining the process for formulating metrics and
standards, and even strengthens the statutory command that the
Federal Railroad Administration and Amtrak work “jointly” to
develop those standards, 2008 Rail Act § 207(a), 49 U.S.C.
§ 24101 note, by eliminating Amtrak’s unilateral ability to
break away from that collaborative process.           And by
preserving the duty to consult with other interested parties,
including the freight railroads, severance of the arbitration
provision would continue the process of obtaining broad input
on the standards.

     In addition, nothing in the statutory text, structure, or
legislative history indicates that Section 207 was meant to be
an all-or-nothing provision or, more to the point, that the
binding-arbitration provision was a legislative deal-breaker.
                                 20
Cf. Brockett v. Spokane Arcades, Inc., 472 U.S. 491, 506
(1985) (holding that severance is impermissible where there is
evidence that the legislature “would not have passed it had it
known the challenged provision was invalid”).

     Fourth, the Railroad Association argues that the
government waived its ability to argue for severance by waiting
until we remanded to the district court to first propose
severance of Section 207(d). That argument fails. To begin
with, the question of severance arises only after a statute has
been held unconstitutional. It is thus unsurprising that the
government devoted its efforts to vigorously defending the
constitutionality of the 2008 Rail Act, and did not broach the
severability question until the remedial stage of this litigation.
The cases on which the Railroad Association relies fall wide of
the mark since they involve instances in which the question of
severability was not raised at all in the appellate briefing.3

     In any event, severability is a doctrine borne out of
constitutional-avoidance principles, respect for the separation
of powers, and judicial circumspection when confronting
legislation duly enacted by the co-equal branches of
government. Parties cannot, by litigation tactics or oversight,

     3
       Even assuming that we would agree with these out-of-circuit
decisions, they arose in a very different procedural posture. See,
e.g., Centro de la Comunidad Hispana de Locust Valley v. Town of
Oyster Bay, 868 F.3d 104, 118 (2d Cir. 2017) (parties expressly
sought invalidation of an entire ordinance, not severance);
Telecommunications Regulatory Bd. of Puerto Rico v. CTIA-
Wireless Ass’n, 752 F.3d 60, 63 n.2 (1st Cir. 2014) (noting that the
parties only asked for invalidation of an Act “in toto” and maintained
that argument on appeal); Lozano v. City of Hazleton, 620 F.3d 170,
182 (3d Cir. 2010) (finding a severability argument waived only
because no party contested the district court’s failure to sever),
vacated by City of Hazelton v. Lozano, 563 U.S. 1030 (2011).
                               21
compel the courts to strike down more of a law than the
Constitution or statutory construction principles demand.

    For all of those reasons, we hold that the proper
constitutional remedy in this case is to sever Section 207(d)’s
binding-arbitration provision and leave the balance of Section
207 and the 2008 Rail Act intact.

                                C

     When the Supreme Court remanded this case, it left open
for this court’s consideration a separate constitutional question:
whether the appointment of Amtrak’s president by its Board
and not the President violates the Appointments Clause, given
that Amtrak’s president had a vote in establishing the metrics
and standards. American Railroads II¸135 S. Ct. at 1234; see
2008 Rail Act § 202(a), Pub. L. No. 110-432, 122 Stat. at 4911.
In American Railroads III, this court found it unnecessary to
resolve that question given the separate determination that the
statutory scheme stepped over the Due Process Clause line.
821 F.3d at 23.

     The Railroad Association has raised the issue again in this
appeal. We cannot answer that question because it is now
moot. See Iron Arrow Honor Society v. Heckler, 464 U.S. 67,
70 (1983). The May 2010 metrics and standards in which
Amtrak’s president had a role have already been vacated by the
district court, and that unappealed aspect of the district court’s
decision is final. Nor does the Railroad Association face any
forward-going risk of such an allegedly unconstitutional
intrusion into the rulemaking process because Congress
amended the statute in 2015 to require that the voting members
of Amtrak’s Board be appointed by the President and
confirmed by the Senate. 49 U.S.C. § 24302(a)(1). As a
                               22
result, the Railroad Association’s Appointments Clause claim
is moot, and we lack jurisdiction to address it.

                      *    *    *    *   *

     We at long last come to the end of the tracks in this lengthy
litigation.   We hold that the constitutional violations
previously identified by this court can be fully remedied by
excising the binding-arbitration provision in Section 207(d) of
the 2008 Rail Act, and that Section 207(d) is properly
severable. The Railroad Association’s Appointments Clause
challenge is moot. We accordingly reverse the judgment of
the district court and remand for the entry of judgment
consistent with this opinion.

                                                     So ordered.
     TATEL, Circuit Judge, dissenting: Two years ago, this
court held that the Passenger Rail Investment and Improvement
Act of 2008 (the “2008 Rail Act”) “violates due process”
because it “endows Amtrak with regulatory authority over its
competitors.” Ass’n of American Railroads v. United States
Department of Transportation (American Railroads III), 821
F.3d 19, 34 (D.C. Cir. 2016). Adhering faithfully to that
holding, the district court fit the remedy to the flaw by
invalidating Section 207 of the Act—the section that authorizes
Amtrak to work with the Federal Railroad Administration to
develop passenger-rail performance metrics and standards that,
we explained, impose enforceable obligations on Amtrak’s
competitors. See id. at 32–34. Case closed? Apparently not.
According to my colleagues, the district court ought to have
discerned from this court’s prior opinion that “the linchpin for
Amtrak’s ability to unconstitutionally exercise regulatory
authority” somehow lies in a discrete, never-used statutory
subsection that authorizes an independent arbitrator
unaffiliated with Amtrak to take the reins if Amtrak and the
Administration fail to reach agreement on the content of the
metrics and standards. Majority Op. at 8. Properly read, my
colleagues hold, the prior opinion ruled only that “the Due
Process Clause does not allow Amtrak to use an arbitration
process to impose its preferred metrics and standards on its
competitors,” id. at 2 (emphasis added), such that the district
court could—indeed should—have responded to the ruling by
invalidating only the arbitration provision. Were our prior
holding that narrow, I would agree that the district court was
obliged to confine its declaratory remedy to the arbitration
provision. In my view, however, our prior panel held that it is
Amtrak’s very participation in developing the metrics and
standards under the Act—and not just the possibility that
Amtrak might ultimately invoke the Act’s arbitration
provision—that contravenes due process. I would therefore
affirm the district court’s order invalidating Section 207 in full.
                                2
                                I.
     Because understanding the background of this litigation,
including the terms of the 2008 Rail Act and the specific
challenges leveled against its constitutionality, will help
readers to grasp the breadth of our prior holding, I begin with
that background.

     Congress enacted the 2008 Rail Act, Pub. L. No. 110-432,
Div. B, 122 Stat. 4848, 4907, to address the “poor service,
unreliability, and delays” that have historically dogged
Amtrak’s operations, Department of Transportation v. Ass’n of
American Railroads (American Railroads II), 135 S. Ct. 1225,
1229 (2015). Central to this goal, Section 207 of the Act
establishes, over the course of its four subsections, the
regulatory regime at issue in this case. See 2008 Rail Act § 207,
122 Stat. at 4916–17 (codified at 49 U.S.C. § 24101 note). That
regime’s substantive core, laid out in subsection 207(a), is its
requirement that Amtrak and the Department of
Transportation’s Federal Railroad Administration (the
“Administration”) “jointly . . . develop new or improve
existing metrics and minimum standards for measuring the
performance and service quality of intercity passenger train
operations,” according to criteria such as cost-effectiveness and
punctuality. 2008 Rail Act § 207(a). Although these metrics
and standards principally regulate Amtrak’s own operations,
the freight railroads that host Amtrak’s trains on their privately
owned tracks can be liable for damages if their failure to
“provide preference to Amtrak over freight transportation”
causes Amtrak to fall short of the designated standards. 49
U.S.C. § 24308(f)(2); see also id. § 24308(c) (establishing
private carriers’ obligation to give preference to Amtrak).

     Section 207’s remaining three subsections facilitate the
creation and implementation of the jointly authored metrics and
standards envisioned in subsection 207(a). Subsection 207(b)
                               3
requires the Administration to produce a quarterly report on
Amtrak’s performance under the metrics and standards. 2008
Rail Act § 207(b). Subsection 207(c) provides that the metrics
and standards must, as far as practicable, be “incorporate[d]”
into Amtrak’s service agreements with private track-owners.
Id. § 207(c). And subsection 207(d) provides that if Amtrak
and the Administration cannot agree on the content of the
metrics and standards, either party may request that the Surface
Transportation Board appoint an arbitrator to “assist the parties
in resolving their disputes through binding arbitration.” Id.
§ 207(d).

     In 2010, Amtrak and the Administration, without resort to
arbitration, developed the metrics and standards required by the
Act. See Metrics and Standards for Intercity Passenger Rail
Service under Section 207 of the Passenger Rail Investment
and Improvement Act of 2008, 75 Fed. Reg. 26,839 (May 12,
2010). Shortly thereafter, the Association of American
Railroads (the “Railroad Association”) initiated this now six-
and-a-half-year-old suit in federal district court. Drawing no
distinctions among the Act’s various subsections, the Railroad
Association contended that Section 207 violates due process by
“[v]esting the coercive power of the government in interested
private parties,” i.e., Amtrak, and also contravenes
constitutional separation-of-powers principles by “placing
legislative and rulemaking authority in the hands of a private
entity that participates in the very industry it is supposed to
regulate.” Complaint at 16–17, Ass’n of American Railroads v.
Department of Transportation, 865 F. Supp. 2d 22 (D.D.C.
2012) (No. 1:11-cv-01499). As redress, the Railroad
Association sought vacatur of the metrics and standards, as
well as “an order declaring that Section 207”—in its entirety—
“is unconstitutional.” Id. at 3.
                                4
     The district court granted summary judgment to the
government, and the Railroad Association appealed, renewing
its argument that “Amtrak’s involvement in developing the
metrics and standards” violates due process. Ass’n of American
Railroads v. Department of Transportation (American
Railroads I), 721 F.3d 666, 677 (D.C. Cir. 2013). We had no
need to address that argument, however, because we held
Section 207 unconstitutional on the alternative theory that it
violates separation-of-powers principles by vesting regulatory
authority in a “private corporation.” Id. But after the Supreme
Court vacated and remanded, holding that “for purposes of
determining the validity of the metrics and standards, Amtrak
is a governmental entity,” American Railroads II, 135 S. Ct. at
1228, we returned to the previously unresolved due-process
issue.

     On that issue, we held that the 2008 Rail Act “violates the
Fifth Amendment’s Due Process Clause by authorizing an
economically self-interested actor to regulate its competitors.”
American Railroads III, 821 F.3d at 23. Reasoning that “the
due process of law is violated when a self-interested entity is
‘intrusted with the power to regulate the business . . . of a
competitor,’” id. at 31 (alteration in original) (quoting Carter
v. Carter Coal Co., 298 U.S. 238, 311 (1936)), we asked
whether “Amtrak is (1) a self-interested entity (2) with
regulatory authority over its competitors,” id. As long as
Section 207 remains in the picture, we held, the answer is
“yes.” Emphasizing Amtrak’s statutory duty to maximize
revenues, see 49 U.S.C. § 24101(d), we concluded that Amtrak
is motivated by “economic self-interest” notwithstanding its
governmental character, American Railroads III, 821 F.3d at
32. And, we went on, Section 207 grants Amtrak regulatory
power over its competition because it gives Amtrak “the
authority to develop metrics and standards—constrained very
partially . . . by the [Administration] and the arbitrator,” id. at
                               5
33—and because those metrics and standards “force freight
operators to alter their behavior,” id. at 32.

     We also separately discussed two Appointments Clause
arguments the Railroad Association had added to the mix over
the course of litigation. One was aimed at the makeup of
Amtrak’s board of directors, and the other at the Act’s
arbitration provision, subsection 207(d). Deeming it a “close[]
call” as to whether the Railroad Association had properly
preserved the first of these arguments, we found that “our
ultimate disposition” of the case “d[id] not require us to
consider it.” Id. at 24. But finding the second argument
“properly presented for our review,” id. at 27, we held that
subsection 207(d) is unconstitutional because it empowers an
arbitrator neither appointed through the constitutionally
requisite procedures nor overseen by an officer so appointed
“to render a final decision regarding the content of the metrics
and standards” in the event of a dispute between Amtrak and
the Administration, id. at 37.

     Five months after our mandate issued, the government
moved for entry of final judgment in the district court. Under
the government’s proposed order, the district court would,
consistent with our holding, grant summary judgment to the
Railroad Association and vacate the existing metrics and
standards. But there was a catch. Rather than granting the
Railroad Association the full relief it had sought, including a
declaration that Section 207 is unconstitutional in its entirety,
the proposed order would sever subsection 207(d)—the
arbitration provision—from the remainder of Section 207 and
invalidate only that subsection.

    The district court rejected this gambit as “stand[ing] [the
panel’s decision] on its head.” Ass’n of American Railroads v.
Department of Transportation, No. 1:11-cv-01499, 2017 WL
                                6
6209642, at *2 (D.D.C. Mar. 23, 2017). The prior panel, the
district court explained, “in addressing [subsection 207(d)],
necessarily had the opportunity to find that the [2008 Rail Act]
violated due process only insofar as it incorporated that
subsection. . . . That it did not do so signals that the
constitutional infection spread more broadly.” Id. at *3. At any
rate, the district court concluded, the prior panel’s foregone
opportunity to announce a holding limited to subsection 207(d)
“foreclose[d] [the district court] from repeating [that]
inquir[y]” because “[o]n an issue the Court of Appeals duly
considered, [a district court] will not propose a narrower
possible holding than what it adopted.” Id. Accordingly, the
district court granted summary judgment to the Railroad
Association, vacated the metrics and standards, and declared
Section 207 unconstitutional in its entirety. See id.

                               II.
     The government contends, and this court now agrees, that
the district court committed legal error by declining to limit its
declaratory remedy to subsection 207(d). I see things
differently.

     To begin on a point of agreement, it is well settled that the
district court has “no power or authority to deviate from the
mandate issued by an appellate court.” Independent Petroleum
Ass’n of America v. Babbitt, 235 F.3d 588, 596–97 (D.C. Cir.
2001) (quoting Briggs v. Pennsylvania Railroad Co., 334 U.S.
304, 306 (1948)). Accordingly, the district court is foreclosed
from fashioning a remedy that is “inconsistent with either the
spirit or express terms of [an appellate panel’s] decision.”
Quern v. Jordan, 440 U.S. 332, 347 n.18 (1979). It is likewise
common ground that the prior panel’s judgment binds this
panel no less than it bound the district court. “When there are
multiple appeals taken in the course of a single piece of
litigation, law-of-the-case doctrine holds that decisions
                                7
rendered on the first appeal should not be revisited on later trips
to the appellate court.” Crocker v. Piedmont Aviation, Inc., 49
F.3d 735, 739 (D.C. Cir. 1995). This principle, we have
observed, “encourages uniformity in the application of legal
standards, enhances predictability in decisionmaking,
promotes the interests of judicial efficiency and economy, and
evinces respect for the efforts of earlier [panels] that have
struggled to educe the appropriate legal norms.” Brewster v.
Commissioner, 607 F.2d 1369, 1373–74 (D.C. Cir. 1979) (per
curiam).

     Where my colleagues and I disagree is over the breadth of
our prior panel’s ruling. They believe that the prior panel held
that Section 207 violates due process only insofar as it
“allow[s] Amtrak to use an arbitration process to impose its
preferred metrics and standards on its competitors.” Majority
Op. at 2 (emphasis added). Under this reading, the
government’s proposed remedy, which would strip the
arbitration provision from the statute but otherwise leave
Amtrak’s joint role in developing the regulatory scheme that
binds its competitors entirely intact, would indeed be
“[]consistent with” our prior panel’s decision. Quern, 440 U.S.
at 347 n.18. In my view, however, our prior panel’s ruling was
far broader: Section 207’s due-process defect lies in the fact
that it allows Amtrak “to impose its preferred metrics and
standards on its competitors” at all, Majority Op. at 2, whether
by prevailing in a contested arbitration proceeding or simply
by convincing the Administration to adopt its proposals. So
understood, our prior holding permits no remedy short of the
section’s wholesale invalidation.

     In concluding that the 2008 Rail Act violates due process,
our prior panel never suggested that the constitutional flaw
resides in any localized, potentially severable portion of
Section 207—and certainly never breathed so much as a hint
                               8
that it resides in subsection 207(d). Instead, along with
Amtrak’s statutory duty to “maximize its revenues,” 49 U.S.C.
§ 24101(d), the panel cited subsection 207(a), which tasks
“Amtrak, jointly with [the Railroad Association], . . . with
developing the metrics and standards for passenger train
operations, which directly impact freight train operations,” as
one of the “[t]wo undisputed features of the unique Amtrak
scheme [that] set the stage for [the due-process] controversy,”
American Railroads III, 821 F.3d at 27. Having thus trained its
focus on Amtrak’s very participation in the regulatory process,
the panel proceeded to confront the “specific fairness question”
before it: “whether an economically self-interested entity may
exercise regulatory authority over its rivals.” Id. Over the
course of seven pages, the panel determined, (1) “that the due
process of law is violated when a self-interested entity is
‘intrusted with the power to regulate the business . . . of a
competitor,’” id. at 31 (alteration in original) (quoting Carter
Coal, 298 U.S. at 311), (2) that Amtrak’s “economic self-
interest as it concerns other market participants is undeniable,”
id. at 32, and (3) that Section 207 “grants Amtrak, a self-
interested entity, power to regulate its competitors,” id. at 34,
because it “gives Amtrak the authority to develop metrics and
standards—constrained very partially . . . by the
[Administration] and the arbitrator—that increase the risk that
[the Surface Transportation Board] will initiate an
investigation” that could result in a private rail carrier’s
liability, id. at 33. Based on these three determinations, the
panel concluded that the Act “violates due process” because it
“endows Amtrak with regulatory authority over its
competitors.” Id.

     Subsection 207(d),      which allows an independent
arbitrator to play a         regulatory role under certain
circumstances, can hardly    be said to “endow[] Amtrak with
regulatory authority.” Id.   (emphasis added). Quite to the
                                  9
contrary, the panel viewed the arbitrator as a “constrain[t]” on
Amtrak’s regulatory power. Id. at 33. To be sure, in an
alternative holding, the panel also accepted the Railroad
Association’s “other” argument, that Section 207’s arbitration
provision runs afoul of the Appointments Clause. Id. at 36. But
nothing in that discussion suggests that Section 207’s due-
process shortcomings likewise spring from that subsection.

      Three additional considerations reinforce my view that the
prior panel held Section 207 so fundamentally flawed as to be
incapable of judicial salvage. First, not only did the panel
conspicuously decline to signal that any remedial
considerations remained for the district court to address on
remand, but it also declared that although its ruling did not
“foreclose Congress from tapping into whatever creative spark
spawned the Amtrak experiment in public-private enterprise[,]
. . . the Due Process Clause of the Fifth Amendment puts
Congress to a choice: its chartered entities may either compete,
as market participants, or regulate, as official bodies.” Id. (first
emphasis added). Why would the panel have described its
ruling as leaving Congress a choice as to Amtrak’s future role
had it anticipated that the constitutional deficiency could be
addressed without disturbing Section 207’s essential
underpinnings by simply severing subsection 207(d)? Second,
had the panel meant to confine its due-process holding to that
subsection, it surely would have addressed the Railroad
Association’s argument that Amtrak’s board of directors is
“constitutionally [in]eligible to exercise regulatory power.” Id.
at 23. Yet the panel declined to do so, concluding that the case’s
“ultimate disposition” obviated the need to resolve the issue.
Id. at 24. This conclusion is self-explanatory if the panel
believed that the Railroad Association’s victory on the due-
process issue entitled it to the full relief it sought, but not if the
panel’s holding handed the Railroad Association no more than
a partial win. Finally, recall that neither Amtrak nor the
                               10
Administration invoked Section 207’s arbitration provision in
the course of developing the now-vacated 2010 metrics and
standards. Accordingly, the invalidation of that provision alone
would leave Amtrak and the Administration free to follow
exactly the same path they previously traveled and arrive at
exactly the same result. Yet readers would search our prior
opinion in vain for any hint that the metrics and standards that
arose out of “‘[a] statute which . . . undertakes an intolerable
and unconstitutional interference with personal liberty and
private property’ and transgresses ‘the very nature of’
governmental function” might be so easily resuscitated. Id. at
34 (quoting Carter Coal, 298 U.S. at 311).

      Despite the foregoing, and the fact that our prior opinion
says nothing at all about subsection 207(d) over the course of
its seven-page explanation as to why Section 207 “violates due
process,” id. at 34, this court nonetheless reads the opinion to
have “identifie[d] the arbitration provision as the critical
constitutional fissure.” Majority Op. at 10. In support, it points
out that the prior panel, after having explained the basis for its
constitutional conclusion, twice cited the arbitration provision
as part of its explanation as to why “[n]one of the
Government’s numerous counterarguments” altered that
conclusion. American Railroads III, 821 F.3d at 34. These two
fleeting references cannot bear the dispositive weight my
colleagues assign to them.

      Our prior panel first cited subsection 207(d) when
rejecting the government’s argument that the Administration’s
role in promulgating the metrics and standards “operates as an
‘independent check’ on Amtrak’s self-interestedness.” Id. at
35. The panel, however, never identified that subsection as
essential to its reasoning. It wrote, and I quote in full:
                              11
       To be sure, [the 2008 Rail Act] does require
       Amtrak and [the Administration] to “jointly”
       develop the metrics, but it’s far from clear
       whether and in what way [the Administration]
       “checks” Amtrak. Both are subdivisions within
       the same branch and work in tandem to
       effectuate the goals Congress has set. Nowhere
       in the scheme is there any suggestion that [the
       Administration] must safeguard the freight
       operators’ interests or constrain Amtrak’s profit
       pursuits. Moreover, [the Administration] is
       powerless to overrule Amtrak. As joint
       developers, they occupy positions of equal
       authority. When          there is intractable
       disagreement between the two, the matter is
       resolved by an arbitrator, who may ultimately
       choose to side with Amtrak. [The
       Administration] cannot keep Amtrak’s naked
       self-interest in check, and therefore the
       requirement of joint development does not
       somehow sanitize the Act.

Id. (emphasis added) (footnote and citation omitted). My
colleagues construe this passage as holding that, absent the
arbitration provision, the 2008 Rail Act would pass
constitutional muster by allowing for “the controlling
intermediation of a neutral federal agency.” Majority Op. at 11.
But this reading leapfrogs over the panel’s principal concern—
reread the first three sentences—that the Administration is not
a “neutral federal agency,” id., to focus exclusively on the
panel’s secondary rationale, hanging on by a “moreover,” for
holding that the Administration’s involvement does not cure
the Act’s due-process deficiencies. Certainly, as my colleagues
point out, see id. at 16, our prior panel noted that the
Administration would be “presumptively disinterested” if left
                               12
to develop the metrics and standards “alone,” American
Railroads III, 821 F.3d at 35 (emphasis added) (quoting Carter
Coal, 298 U.S. at 311). But the panel doubted the
Administration’s ability to remain impartial under the actual
joint scheme at issue here, given that Section 207 requires the
Administration to “work in tandem” with a self-interested
“subdivision[] within the same branch” to regulate parties
whose interests neither regulator has any incentive to
“safeguard.” Id.

     The panel’s second (and final) reference to
subsection 207(d) in the due-process context appears in a
footnote distinguishing a line of cases, including Currin v.
Wallace, 306 U.S. 1 (1939), and Sunshine Anthracite Coal Co.
v. Adkins, 310 U.S. 381 (1940), in which “the [Supreme] Court
has upheld arrangements under which regulatory burdens can
be imposed by the joint action of a self-interested group and a
government agency.” American Railroads III, 821 F.3d at 34
n.4. The panel believed that these cases were “inapplicable” to
Amtrak’s position “because [the Administration’s] authority to
hold the line against overreaching by Amtrak is undermined by
the power of the arbitrator.” Id. But the mere fact that the panel
found subsection 207(d) sufficient to distinguish the statutory
scheme at issue here from those upheld in Currin and Adkins
hardly suggests that, under the panel’s theory of
unconstitutionality, those cases would govern but for that
subsection. Indeed, prior to this case’s run up to the Supreme
Court, that same panel in an earlier opinion found that
Section 207 bore only “a passing resemblance to the humbler
statutory frameworks in [Currin] and [Adkins]” and went on to
distinguish those cases on grounds entirely unrelated to the
arbitration provision. American Railroads I, 721 F.3d at 671;
see also id. (noting that “[t]he industries in Currin,” unlike
Amtrak, “did not craft [industry] regulations” but merely had
the opportunity to vote on whether to approve agency-written
                               13
regulations, and that “the agency in Adkins could unilaterally
change regulations proposed to it by private parties, whereas”
under the Act, “Amtrak enjoys authority equal to” the
Administration’s). The ready availability of alternate grounds
for distinguishing Currin and Adkins strongly counsels against
reading the panel’s cursory, footnoted treatment of these cases
to suggest that the due-process violation we held to inhere in
Amtrak’s “coercive regulatory power” under the Act,
American Railroads III, 821 F.3d at 34, could somehow be
cured by removing an independent “constrain[t]” on that
power, id. at 33.

     The broader point is this: these two references to
subsection 207(d) nowhere suggest that removing the arbitrator
as the final decision-maker, and thereby effectively allowing
the Administration to veto Amtrak’s regulatory proposals,
would render Section 207 constitutional. Even accepting, as do
my colleagues, that these references can be read together to
establish our prior panel’s acknowledgment that the
Constitution would not “prohibit Amtrak from exercising some
measure of joint control with a disinterested governmental
agency, as long as that agency’s duty to protect the ‘public
good’ could check Amtrak’s self-interest,” Majority Op. at 10
(quoting American Railroads III, 821 F.3d at 29), we cannot
ignore the panel’s express determination that the
Administration is neither disinterested nor tasked with
“constrain[ing] Amtrak’s profit pursuits,” American Railroads
III, 821 F.3d at 35, or acting as “a steward for the interests of
freight operators” that are bound by the Amtrak-influenced
metrics and standards, id. at 35 n.5. The “government’s
increasing reliance on public-private partnerships,” the panel
explained, “portends an . . . ill-fitting accommodation between
the exercise of regulatory power and concerns about fairness
and accountability.” Id. at 31. Even if, as my colleagues see it,
subsection 207(d) “empowered Amtrak to impose on its
                               14
competitors rules formulated with its own self-interest in mind”
because “[a]ll Amtrak had to do was persuade the arbitrator to
rule in its favor,” Majority Op. at 11, removing that subsection
would do nothing to satisfy our prior panel’s concern that
Amtrak could easily persuade the Administration to accede to
its self-interested demands. After all, the Administration, more
so than an independent arbitrator, lacks any structural incentive
to stand up to Amtrak, a “subdivision[] within the same
branch.” American Railroads III, 821 F.3d at 35.

     To the contrary, and for the reasons I have already given,
removing subsection 207(d) would not correct the due-process
deficiencies our prior panel perceived in Section 207. Put
simply, the panel held that Section 207 violates due process
because it allows “a self-interested entity” to exercise
“regulatory authority over its competitors.” American
Railroads III, 821 F.3d at 31. The panel nowhere indicated that
the arbitration provision renders Amtrak any more self-
interested than it otherwise would be, and, far from viewing
that provision as effectuating Amtrak’s regulatory authority,
the panel described the provision as a “constrain[t]” on that
authority. Id. at 33. To be sure, as my colleagues point out, the
prior panel, in so characterizing the arbitration provision,
referenced its later “discuss[ion]” of Currin and Adkins.
Majority Op. at 15 (quoting American Railroads III, 821 F.3d
at 33). But nothing in that discussion says that the statutory
subsection that “constrain[s]” Amtrak’s regulatory authority is,
paradoxically, the very source of that authority. American
Railroads III, 821 F.3d at 33.

     In my view, then, the district court correctly concluded that
the government’s proposed remedy would not address the 2008
Rail Act’s constitutional flaws as the prior panel explained
them. My colleagues are able to arrive at the opposite
conclusion only by imputing to our prior panel a far narrower
                               15
theory of Section 207’s unconstitutionality than it ever
endorsed or even suggested.

                              III.
      The court today emphasizes the “grav[ity]” of invalidating
a duly enacted statute and our duty as the judiciary to do as
little damage as possible to the work of the elected branches of
government. Majority Op. at 9. “[W]hen a constitutional
question must be joined,” my colleagues observe, “courts must
choose the narrowest constitutional path to decision.” Id. But
these important concerns, which I share, also bound our prior
panel. See El Paso & Northeastern Railway Co. v. Gutierrez,
215 U.S. 87, 96 (1909) (“[W]henever an act of Congress
contains unobjectionable provisions separable from those
found to be unconstitutional, it is the duty of [a] court to so
declare . . . .” (emphasis added)). Out of “respect for [its]
efforts,” Brewster, 607 F.2d at 1373, I would presume that our
prior panel well heeded its obligation to “act cautiously” when
“review[ing] the constitutionality of a legislative Act,” Regan
v. Time, Inc., 468 U.S. 641, 652 (1984) (plurality opinion), and
that its decision not to confine its due-process holding to any
single statutory subsection reflects its considered judgment that
Section 207’s constitutional flaws are fatal to the whole.

      If the government disagrees with this assumption and
believes that our prior panel simply neglected its obligation to
consider whether it could dispose of the Railroad Association’s
due-process challenge on narrower grounds, then it should
have said as much in its petition for rehearing en banc. After
all, if a panel that holds an Act of Congress unconstitutional
fails to consider whether it can cast its holding more narrowly,
it commits an error that may well justify en banc review. See
generally D.C. Cir. R. 35(a) (allowing for en banc review
where a matter “involves a question of exceptional
importance”). But in its en banc petition, the government did
                                16
not argue that the panel should have considered a more targeted
constitutional holding—say, for example, the one this court
adopts today. Had it done so, I might well have voted to rehear
the case en banc. But that argument having never been made
and rehearing en banc having been denied, we are now bound
by that panel’s holding—whatever we think of it. See, e.g.,
United States v. Kolter, 71 F.3d 425, 431 (D.C. Cir. 1995)
(“This panel would be bound by [a prior panel’s] decision even
if we did not agree with it.”); Ass’n of Civilian Technicians,
Montana Air Chapter v. FLRA, 756 F.2d 172, 176 (D.C. Cir.
1985) (stare decisis principles “would be undermined if
previous decisions were open to reconsideration merely
because they were debatable”).

     Once our prior panel’s opinion became final, the “legal
donnybrook over the bounds of congressional power” that this
case once posed came to an end. Majority Op. at 2. The only
task that remained for the district court was to enter relief that
honored this court’s binding resolution of the legal issues in
play. Because I believe the district court fulfilled its obligation,
giving our prior panel’s opinion its most natural reading, I
respectfully dissent.
