                       FOR PUBLICATION

    UNITED STATES COURT OF APPEALS
         FOR THE NINTH CIRCUIT


 LINDA JACKIE LARSON, Personal                         No. 18-35985
 Representative of the Estate of
 Kenneth Earl Larson,                                    D.C. No.
                   Plaintiff-Appellant,               4:17-cv-00110-
                                                            JTJ
                       v.

 ANDREW M. SAUL, Commissioner of                         OPINION
 Social Security,
                  Defendant-Appellee.

         Appeal from the United States District Court
                 for the District of Montana
        John T. Johnston, Magistrate Judge, Presiding

           Argued and Submitted November 7, 2019
                      Portland, Oregon

                         Filed July 21, 2020

       Before: Ronald Lee Gilman, * Richard A. Paez,
         and Johnnie B. Rawlinson, Circuit Judges.

                       Opinion by Judge Paez


     *
       The Honorable Ronald Lee Gilman, United States Circuit Judge
for the U.S. Court of Appeals for the Sixth Circuit, sitting by designation.
2                        LARSON V. SAUL

                          SUMMARY **


                          Social Security

     The panel affirmed the Commissioner of Social
Security’s reduction of a claimant’s social security
retirement benefits pursuant to the Windfall Elimination
Provision (WEP) of the Social Security Act.

    When claimant retired from his position as a full-time
dual-status military technician, he was eligible for three
types of retirement benefits: a civil service retirement system
pension, a military pension, and social security retirement
benefits. Dual-status technicians are members of the armed
forces who are assigned to work in civilian positions. The
WEP provision applies to retirees, like the claimant, who are
entitled to social security benefits and pension benefits from
employment not covered by social security. Claimant
argued that an exception to the WEP – the uniformed
services exception – applied to him, and shielded his benefits
from reduction under the WEP.

    The panel held that the text of the uniformed services
exception to WEP was ambiguous as applied to dual-status
technicians. The panel further held that the Commissioner’s
interpretation of the uniformed services exception was
reasonable, and was entitled to deference under Skidmore v.
Swift & Co., 323 U.S. 134 (1944). The panel, therefore,
affirmed the Social Security Administration’s WEP
reduction of claimant’s social security retirement benefits.


    **
       This summary constitutes no part of the opinion of the court. It
has been prepared by court staff for the convenience of the reader.
                       LARSON V. SAUL                       3

                        COUNSEL

William O. Bronson (argued), William O. Bronson PLLC,
Great Falls, Montana, for Plaintiff-Appellant.

Sushma Soni (argued) and Alisa B. Klein, Appellate Staff;
Kurt G. Alime, United States Attorney; Joseph H. Hunt,
Assistant Attorney General; Civil Division, United States
Department of Justice, Washington, D.C.; for Defendant-
Appellee.


                         OPINION

PAEZ, Circuit Judge:

     Kenneth E. Larson enlisted in the Montana Air National
Guard in 1971. Just over a year later, he began working as a
full-time dual-status military technician, a role that he held
until his retirement in 2004. Dual-status technicians are
federal civilian employees who are required to maintain
membership in the Selected Reserve. See 10 U.S.C.
§ 10216(a).     Larson also occasionally participated in
inactive-duty training and was deployed overseas, for which
he received separate military pay.           See 37 U.S.C.
§§ 204(a)(1), 206; 10 U.S.C. §§ 12731–41. Upon his
retirement, Larson was eligible for three types of retirement
benefits: a civil service retirement system (CSRS) pension,
a military pension, and social-security retirement benefits.

    At issue in this case is the manner in which the Social
Security Administration (SSA) calculated Larson’s social-
security benefits. The SSA awarded Larson benefits, but
reduced them pursuant to the Windfall Elimination
Provision (WEP) of the Social Security Act, 42 U.S.C.
§§ 401 et seq. That provision applies to retirees who, like
4                     LARSON V. SAUL

Larson, are entitled to social-security benefits and pension
benefits from employment not covered by social security.

    There are, however, exceptions to the WEP. Larson
argues that one such exception—the uniformed-services
exception—shields his benefits from reduction under the
WEP. The exception applies to “a payment based wholly on
service as a member of a uniformed service.” 42 U.S.C.
§ 415(a)(7)(A)(ii)(III). Larson contends that he is entitled to
the uniformed-services exception because he was required to
serve in the National Guard (a uniformed service) for the
duration of his employment as a dual-status technician.

    Larson raised this argument with the SSA and requested
reconsideration of the reduction. On reconsideration, the
Commissioner rejected Larson’s argument, and an
administrative law judge affirmed. Larson then sought
judicial review in the District Court for the District of
Montana. The court agreed with the Commissioner that the
uniformed-services exception did not apply and entered
judgment for the Commissioner. Larson now appeals, again
arguing that the SSA erred in applying the WEP to reduce
his retirement benefits.

    We conclude that the text of the uniformed-services
exception is ambiguous as applied to dual-status technicians.
But, because the Commissioner’s interpretation of the
uniformed-services exception is reasonable, it is entitled to
deference under Skidmore v. Swift & Co., 323 U.S. 134
(1944). We therefore affirm the SSA’s reduction of Larson’s
social-security retirement benefits.
                         LARSON V. SAUL                             5

                                  I.

                                 A.

    The Social Security Act provides retirement benefits for
eligible individuals age 62 and older. 42 U.S.C. § 402(a). In
its calculation of benefits, the SSA distinguishes between
two types of employment: “covered” and “non-covered”
employment. Covered employees pay social-security taxes
and are entitled to social-security retirement benefits on their
earnings; noncovered employees do not pay social-security
taxes and are not entitled to social-security benefits. See Das
v. Dep’t of Health & Human Servs., 17 F.3d 1250, 1253–55
(9th Cir. 1994); see also 42 U.S.C. § 410; 20 C.F.R.
§§ 404.1003–38 (2016). Noncovered employees who work
in the public sector may still participate in a pension plan
like the CSRS and receive a pension upon retirement. See
Das, 17 F.3d at 1253.

     Social-security benefits are calculated on the basis of
retirees’ lifetime earnings. Retirees who earned lower
average monthly incomes receive a higher percentage of
their earnings than retirees who earned higher average
monthly incomes. This progressive pay-out system is
intended to balance benefit adequacy with equity for
retirees. 1 Before 1983, retirees who had earnings from both
covered and noncovered employment could receive
unusually high windfall payments because they were eligible
for both social-security retirement benefits and a pension
from an employer who did not withhold social-security

    1
       See Andrew G. Biggs, Mark Sarney, and Christopher R.
Tamborini, A Progressivity Index for Social Security, Office of Ret. &
Disability Pol’y, Soc. Sec. Admin. (2009), http://www.ssa.gov/policy/d
ocs/issuepapers/ip2009-01.html (last visited July 10, 2020).
6                     LARSON V. SAUL

taxes. These retirees had their social-security retirement
benefits calculated using the higher-percentage return
intended for workers with lower lifetime covered
employment, but also received a separate pension from their
noncovered employment. The combined benefits often
exceeded the social-security benefit paid to a retiree who had
similar earnings under covered employment.

     To eliminate this windfall, Congress passed the WEP,
42 U.S.C. § 415(a)(7). The WEP reduces the social-security
benefits of individuals who earn a pension from noncovered
employment and qualify for covered-employment
retirement benefits. See Social Security Administration
Publication No. 05-10045, Windfall Elimination Provision
(2020).

   There are, however, statutory exceptions to the WEP.
One of these exceptions is the “uniformed-services
exception.” This provision excludes from the WEP

       a payment based wholly on service as a
       member of a uniformed service (as defined in
       section 410(m) of this title) which is based in
       whole or in part upon his or her earnings for
       service      which     did     not    constitute
       “employment” as defined in section 410 of
       this title for purposes of this subchapter[.]

42 U.S.C. § 415(a)(7)(A)(ii)(III). A “member of uniformed
service” is defined in section 410(m) as

       [a]ny person appointed, enlisted, or inducted
       in a component of the Army, Navy, Air
       Force, Marine Corps, or Coast Guard
       (including a reserve component as defined in
       section 101(27) of title 38), or in one of those
                          LARSON V. SAUL                               7

         services   without              specification       of
         component[.]

    Congress enacted the exception to the WEP in order to
address an anomaly in military service pensions. Before its
passage, most categories of military service were already
classified as covered employment and did not implicate the
WEP or were expressly exempt.               See 42 U.S.C.
§§ 415(a)(7)(B)(i), 410(l)(1)(A)–(B).       Active military
service was classified as covered employment under the
Social Security Act in 1957, and inactive duty by reservists
became covered in 1988. See H.R. Rep. No. 103-670, at 125
(1994) (Conf. Rep.), as reprinted in 1994 U.S.C.C.A.N.
1553. A pension based on either type of service, therefore,
if performed before 1957, did not trigger the WEP. Id. The
only military pension that triggered the WEP before the
passage of the uniformed-services exception was a pension
based on inactive duty completed between 1956 and 1988.
Id. The passage of the exception conformed the treatment of
individuals receiving inactive-duty pensions based on
service between 1956 and 1988 with the treatment of all
other military retirees.

                                 *   *     *

   Kenneth E. Larson 2 (“Larson”) worked as an enlisted
member of the Montana Air National Guard for thirty-five
years. He received military pay for his part-time inactive-
duty National Guard drills and training, which took place on
weekends and during annual field trainings, and for his full-
time active deployments. Nineteen months after enlisting,

    2
     Linda Jackie Larson, the personal representative of Larson’s estate,
was substituted for Larson in the present litigation because he passed
away in July 2019.
8                     LARSON V. SAUL

Larson began working for the Montana National Air Guard
as a full-time dual-status military technician.

    Dual-status technicians are members of the armed forces
who are assigned to work in civilian positions. See
10 U.S.C. § 10216(a). They may help organize, administer,
instruct, or train members of the National Guard, or they help
maintain and repair supplies or equipment issued to the
reserve or other armed forces. Id. § 10216(a)(C). The job
requires that they also satisfy various military-service
requirements: they must participate in inactive-duty training,
wear a uniform, comply with military standards of conduct,
meet physical requirements, and must be available for active
deployment. Importantly, dual-status technicians must
maintain membership in the National Guard for the duration
of their employment. See 32 U.S.C. § 709(b); 10 U.S.C.
§ 10216(a).

     After Larson retired in 2004, he began receiving his
federal CSRS pension. Larson was also eligible for social-
security retirement benefits because he paid social-security
taxes on the military pay he earned while he served on
inactive-duty training, active duty, and on his non-
governmental civilian employment.           See 37 U.S.C.
§§ 204(a)(1), 206; 10 U.S.C. §§ 12731–41. Upon his
retirement, then, Larson was entitled to two separate
pensions: (1) his CSRS pension, based on his thirty-two
years of noncovered earnings as a dual-status technician, and
(2) his military pension, based on his thirty-five years of
military service in the Montana Air National Guard. His
military retirement benefits are plainly exempt from the
WEP, either because his military service qualifies as covered
employment under the Social Security Act, or because those
benefits were based on Larson’s membership in a uniformed
service.
                     LARSON V. SAUL                        9

    Larson was also eligible for social-security retirement
benefits, which he applied for in early 2015. The same
month, SSA notified Larson that he would receive reduced
benefits because his employment as a technician was subject
to the WEP. The SSA explained that Larson’s monthly
benefits would be reduced because he was entitled to “both
Social Security and a pension based on work that is not
covered by Social Security.” In other words, the pension that
Larson received from his employment as a dual-status
technician was not “based wholly on service as a member of
a uniformed service” within the meaning of 42 U.S.C.
§ 415(a)(7)(A)(ii)(III).

    Larson sought reconsideration of the benefits
determination, but the SSA again concluded that the WEP
reduction applied. He then requested a hearing before an
ALJ, who affirmed the Commissioner’s decision. The ALJ
explained that the “SSA interprets the uniformed-services
exception to the WEP to mean that only monthly payments
based on military service are exempt,” and so payments
received by dual-status technicians are not exempt because
they “are based on noncovered civilian public employment.”

    The ALJ’s decision became the final decision of the
Commissioner after the Appeals Council declined to review
it. Larson then sought judicial review in the District Court
for the District of Montana. The court agreed that Larson’s
social-security retirement benefits were subject to the WEP
and entered judgment in favor of the Commissioner. See
Larson v. Berryhill, No. CV 17-110-GF-JTJ (D. Mont. Sept.
26, 2018).

   The single question presented on appeal is the same as
the question presented to the district court: whether
payments made to a dual-status technician under a CSRS
pension qualify as “payments based wholly on service as a
10                         LARSON V. SAUL

member of a uniformed service” for purposes of the
uniformed-services exception, thereby exempting Larson’s
social-security retirement benefits from the WEP.

                                    B.

    Four of our sister circuits have considered and answered
the question before us. The Eighth Circuit held in Petersen
v. Astrue, 633 F.3d 633 (8th Cir. 2011), that the WEP
reduction did not apply to benefits payments received by a
dual-status technician occupying a hybrid civilian and
National Guard role. Id. at 637–38. The court explained that
the plain language of the uniformed-services exception
suggests that it applies to all service performed as a member
of a uniformed service. Id. at 637. Because service
technicians are required to maintain membership in the
National Guard, and the National Guard is a uniformed
service, the court reasoned that a technician’s civil-service
pension is based on work completed “by” a member of the
uniformed service. Id. at 637–38. The court concluded that
it would not “read a ‘military duty’ requirement into the
statute” where that requirement was not clear from the
statute’s plain language. Id. at 637.

    Shortly after the Eighth Circuit’s decision in Petersen,
the SSA issued an “acquiescence ruling.” 3 The ruling binds
internal components of the SSA but does not have the force
or effect of law. It summarizes Petersen’s holding and



     3
      Acquiescence rulings “explain how [SSA] will apply a holding”
by a United States Court of Appeals that the SSA “determine[s] conflicts
with [its] interpretation of a provision of the Social Security Act . . . or
regulations[.]” 77 Fed. Reg. 51,842, 51,842 (Aug. 27, 2012); see also
20 C.F.R. §§ 404.985(a)–(b), 416.1485.
                        LARSON V. SAUL                            11

briefly describes the SSA’s disagreement with the Eighth
Circuit’s interpretation of the uniformed-services exception:

        We interpret the uniformed services
        exception to the WEP to mean that only
        monthly payments based on military service
        are exempt from the WEP. Under this
        interpretation, monthly payments that are
        based on noncovered civilian public
        employment, including that of National
        Guard technicians who work under the [civil
        service retirement system], are not exempt
        from the WEP.

77 Fed. Reg. at 51,843. The SSA further states that the
legislative history of the WEP “explains that the purpose of
the exception was to exempt military retired pay, based on
noncovered [inactive duty training] military duty, from
application of the WEP. The exception was not intended to
exempt any pension based on civilian work from application
of the WEP.” Id. The ruling concludes that the Petersen
rule is limited to claimants within the Eighth Circuit.

    The SSA also included its interpretation of the
uniformed-services exception in the “Program Operations
Manual System,” 4 (POMS) which describes how to apply
the Petersen rule and addresses various difficulties that
might arise in its implementation (e.g., an eligible individual
moving in or out of the circuit).



    4
      See Social Security Administration, RS 00605.380 National Guard
Civilian Pensions for Dual-status Technicians: Petersen Court Case,
Program Operations Manual (2019).
12                   LARSON V. SAUL

    The Eleventh Circuit, when confronted with the same
issue in Martin v. Social Security Administration
Commissioner, 903 F.3d 1154 (11th Cir. 2018) (per curiam),
reached a different conclusion. Relying on the acquiescence
ruling and the POMS, the court agreed with the SSA that the
uniformed-services exception did not exempt dual-status
technicians from the WEP. The court first concluded that
the uniformed-services exception was ambiguous, because
the word “service” could mean employment generally or
employment specific to military membership. In addition,
the use of “as” in the phrase “based wholly on service as a
member of a uniformed service” appears to limit the WEP
exception to “payments for work performed in one’s
capacity or role as a member of the uniformed services”;
thus, “the work for which Martin now receives civil service
disability retirement payments—his employment as a dual
status technician—must have been performed in his role as
a member of the uniformed service.” Id. at 1164. Because
“Martin did not perform his dual status technician
employment wholly as a member of a uniformed service . . .
[CSRS] payments based on that employment do not qualify
for the exception.” Id. at 1168.

    The Sixth Circuit agreed with the outcome reached by
the Eleventh Circuit, but on different grounds. See Babcock
v. Soc. Sec. Comm’r, 959 F.3d 210 (6th Cir. 2020). The court
explained that the uniformed-services exception, “by its
plain text,” is “cabined to payments that are based
exclusively on employment in the capacity or role of a
uniformed-services member.” Id. at 216. Because dual-
status technicians receive payments not “based exclusively
on employment” performed in a military capacity, the court
held that the exception did not apply. Id. at 217. The Tenth
Circuit agreed with the reasoning and outcome reached by
                     LARSON V. SAUL                       13

the Sixth. See Kientz v. Comm’r, SSA, 954 F.3d 1277, 1285–
86 (10th Cir. 2020).

                           *        *   *

    In concluding that Larson’s CSRS pension payments
were subject to the WEP, the district court relied heavily on
the Eleventh Circuit’s decision in Martin. It held that the
text of the exception was ambiguous, the legislative history
was “not helpful,” and the SSA’s guidance on the issue was
entitled to Skidmore deference.

                               II.

                               A.

    We have jurisdiction over Larson’s appeal from the
district court’s final judgment under 28 U.S.C. § 1291, and
review de novo the district court’s judgment upholding the
Commissioner’s denial of benefits. Harman v. Apfel,
211 F.3d 1172, 1174 (9th Cir.2000). We “must affirm the
Commissioner’s decision if it is supported by substantial
evidence and if the Commissioner applied the correct legal
standards.” Holohan v. Massanari, 246 F.3d 1195, 1201
(9th Cir. 2001).

                               B.

    The SSA urges us to conclude that the uniformed-
services exception unambiguously exempts only payments
based on employment that is entirely military in nature. This
would exclude hybrid civilian-military employment such as
Larson’s position with the Montana National Guard.

    Before deferring to agency interpretation, we
independently examine the text and context of the statute. If
14                    LARSON V. SAUL

the statute—here, the uniformed-services exception—is
unambiguous, we do not defer to the agency’s interpretation.
See High Sierra Hikers Ass’n v. Blackwell, 390 F.3d 630,
638 (9th Cir. 2004). Where Congress has “directly spoken
to the precise question at issue,” and Congress’s intent is
clear, “that is the end of the matter.” Campos-Hernandez v.
Sessions, 889 F.3d 564, 568 (9th Cir. 2018) (quoting
Chevron, U.S.A., Inc v. Nat. Res. Def. Council, Inc., 467 U.S.
837, 842 (1984)).

    Our analysis differs, however, if we deem the statutory
provision at issue to be ambiguous. But before concluding
that the statute is ambiguous, we “exhaust all the ‘traditional
tools’ of construction.” Kisor v. Wilkie, 139 S. Ct. 2400,
2415 (2019). We evaluate the plain text of the statute, its
object and policy, the law’s surrounding provisions, and the
legislative history of its enactment. Carson Harbor Vill.,
Ltd. v. Unocal Corp., 270 F.3d 863, 877 (9th Cir. 2001);
United States v. Williams, 659 F.3d 1223, 1225 (9th Cir.
2011). Only if genuine ambiguity remains after we have
exhausted all possible interpretative tools at our disposal do
we proceed to the agency’s interpretation.

    The uniformed-services exception to the WEP exempts
from reduction “a payment based wholly on service as a
member of a uniformed service[.]”                 42 U.S.C.
§ 415(a)(7)(A)(ii)(III). The government’s reading of the
statute is plausible. It argues that “payment based wholly on
service as” a military member means “payments for work
performed in one’s capacity or role as a member of the
uniformed services.” Although dual-status technicians
occupy quasi-military roles, they do not perform their daily
work entirely in a military capacity. If Congress had
intended civilian technicians to receive retirement payments
that were exempt from the WEP, the government explains,
                     LARSON V. SAUL                       15

it could have exempted payments “based on service by a
member of a uniformed service[.]”

    But the exception, as Larson notes, does not contain an
explicit military-service requirement. It requires only that
the employment be conducted as a member of a uniformed
service. Dual-status technicians are required to maintain
membership in a uniformed service as a condition of their
employment, so every task that they conduct in their capacity
as technicians is technically completed as a member of a
uniformed service.

    The addition of the word “wholly,” however, supports
the SSA’s interpretation. “Wholly on service” suggests that
exempted payments must be based on work performed
wholly in one’s military capacity. If Congress intended the
statute to apply to work performed by employees required to
hold membership in uniformed-services positions, it could
have exempted payments “based on service” or “based on
any service” performed “as a member of a uniformed
service.” Under Larson’s reading, “wholly” is surplusage.
See, e.g., Chicksaw Nation v. United States, 534 U.S. 84
(2001) (“[E]very clause and word of a statute should if
possible, be given effect.”) (internal quotation marks
omitted).

    Larson argues that even if the exception requires that
work be performed in a military capacity, the technician role
is sufficiently military in nature to qualify. In addition to
holding membership in the National Guard, Larson was
required to participate in inactive-duty training, wear a
military uniform while he worked, comply with military
standards of conduct, meet military physical-fitness
standards, and remain available for active military
deployment.
16                     LARSON V. SAUL

    He cites various cases describing how we and other
federal courts have treated the dual-status technician role in
other contexts. We have, for example, analyzed the dual-
status technician role in considering whether a technician
could overcome the doctrine of intra-military immunity and
bring a Title VII suit. See Zuress v. Donley, 606 F.3d 1249,
1254 (9th Cir. 2010). We explained that “dual-status
technicians have long been recognized as ‘civilian
employees whose positions require that they also serve in the
military reserves.’” Id. (quoting Williams v. Wynne,
533 F.3d 360, 367 (5th Cir.2008)). But absent “a clear
statement . . . from Congress to override our settled judicial
doctrine of intra-military immunity,” we held that the roles
occupied by dual-status technicians were sufficiently
military to bar them from suing under Title VII. Id. at 1255.

    Many courts have described the dual-status technician
role as “irreducibly military in nature.” See Leistiko v. Stone,
134 F.3d 817, 820–21 (6th Cir. 1998); see also, e.g., Stauber
v. Cline, 837 F.2d 395, 399 (9th Cir. 1988) (“Although the
technicians had dual status for some purposes, . . . military
regulations, standard operating procedures, and active-duty
military officers controlled how the shop was run.”); Wright
v. Park, 5 F.3d 586, 588–89 (1st Cir. 1993) (“We, too,
conclude that, since National Guard technicians’ positions
are encompassed within a military organization and require
the performance of work directly related to national defense,
such positions are themselves military in nature.”); Illinois
Nat. Guard v. Fed. Labor Relations Auth., 854 F.2d 1396,
1398 (D.C. Cir. 1988) (“While many of their duties are
similar to those of employees who work in a typical civilian
setting, technicians traditionally have been required to be
members of their state National Guard units, and must
perform even their civilian tasks in a distinctly military
context, implicating significant military concerns.”)
                      LARSON V. SAUL                       17

(internal quotation marks omitted). Other courts, however,
have expressed doubt. See, e.g., Klotzbach v. Callaway,
473 F. Supp. 1337, 1342–43 (W.D.N.Y. 1979) (“[T]he
uniform requirement will not destroy the civilian
characteristics of technicians’ positions because they will
remain entitled to federal civil service benefits.”).

    The dual-status technician statute defines the role as
civilian. They are “Federal civilian employee[s]” who “shall
be authorized and accounted for as a separate category of
civilian employees.” 10 U.S.C. § 10216(a), (b). Dual-status
technicians were initially authorized in 1916, when
Congress reconstituted state militias into the National Guard
and provided funds for the Guard to employ state civilian
employees “for the care of the material, animals, and
equipment thereof.” National Defense Act of 1916, § 90,
39 Stat. 166, 197, 199, 205; see also Act of June 19, 1935,
49 Stat. 391. By 1968, these state civilian employees served
in a variety of different roles in each state’s National Guard
and continued to receive state benefits. The National Guard
Technicians Act of 1968, Pub. L. No. 90-486, 82 Stat. 755
(codified at 32 U.S.C. § 709), converted these employees
into federal employees for purposes of their retirement and
other fringe benefits, but retained state authority over their
supervision. H.R. Rep. No. 90-1823, at 1 (1968), as
reprinted in 1968 U.S.C.C.A.N. 3318, 3319. It appears that
these roles were envisioned and classified as remaining
“outside the competitive service,” 32 U.S.C. 709(e), even
though they support the National Guard.

    The legislative history does not helpfully inform our
reading. It is mostly silent with respect to the pensions of
dual-status technicians. Prior to the adoption of the
uniformed-services exception, the WEP’s modified formula
did not apply to military pensions based on (1) any type of
18                    LARSON V. SAUL

active military service; or (2) inactive duty by reservists
(such as weekend drills) that occurred before 1957 or after
1987. Congress viewed this differential treatment of
pensions based on inactive duty as “arbitrary and
inequitable.”    H.R. Rep. No. 103-506 at 67, 1994
U.S.C.C.A.N. 1520. The uniformed-services exception was
enacted to conform the treatment of inactive-duty military
retirees between 1956 and 1987 with that of other retirees.

    The legislative history could suggest that Congress
intended to bring the pensions of work performed by all
military service members (including dual-status technicians)
into harmony, without regard to the type of duty served. But
because Congress failed to explicitly address dual-status
technicians’ civil-service pensions, it may also have
manifested a desire not to do so. The SSA adopts the latter
position: the history, in its view, “explains that the purpose
of the exception was to exempt military retired pay, based
on noncovered military duty [inactive duty training], from
application of the WEP. The exception was not intended to
exempt any pension based on civilian work from application
of the WEP.” 77 Fed. Reg. at 51,843.

    Both parties argue that the statute unambiguously
supports their interpretation, and both parties present a
plausible interpretation of the statute. The context of the
dual-technician role, the WEP, and the legislative history of
the uniformed-services exception do not resolve the genuine
ambiguity in the text. We therefore conclude that the
exception is ambiguous.

                             C.

   We fully defer to an agency’s interpretation of a statute
under Chevron, U.S.A., Inc v. Nat. Res. Def. Council, Inc.,
467 U.S. 837 (1984), where Congress has “delegated
                      LARSON V. SAUL                       19

authority to the agency generally to make rules carrying the
force of law,” and “the agency interpretation claiming
deference was promulgated in the exercise of that authority.”
United States v. Mead Corp., 533 U.S. 218, 226–27 (2001).
When “full-blown Chevron deference is not due”—either
because Congress has not delegated rulemaking authority to
the agency or the rule in question does not carry the force of
law—courts still owe some deference to reasonable agency
construction of statutes under Skidmore v. Swift & Co.,
323 U.S. 134 (1944). United States v. W.R. Grace & Co.,
429 F.3d 1224, 1237 (9th Cir. 2005). Agencies often make
interpretive choices in applying statutes; those choices are
due deference when they are “well-reasoned views” that
reflect “a body of experience and informed judgment to
which courts and litigants may properly resort for guidance.”
Mead, 533 U.S. at 227 (quoting Skidmore, 323 at 139–40).
The measure of deference owed to an agency interpreting its
own governing statute in the face of ambiguity can range
from very little to fully deferential, depending on the degree
of the agency’s care, consistency, formality, relative
expertise, and the persuasiveness of the agency’s decision.
Id. at 228.

    Chevron and later cases suggest that actions taken after
rigorous vetting procedures and practices carry the force of
law, and actions taken without such formality do not. See
Chevron, 467 U.S. at 842–44; Mead, 533 U.S. at 230 (“It is
fair to assume generally that Congress contemplates
administrative action with the effect of law when it provides
for a relatively formal administrative procedure tending to
foster the fairness and deliberation that should underlie a
pronouncement of such force.”). For this reason, policy
statements, agency manuals, and enforcement guidelines do
not carry the force of law and are not entitled to Chevron
20                        LARSON V. SAUL

deference. Christensen v. Harris Cnty., 529 U.S. 576, 587
(2000).

    Congress delegated to the SSA the authority to make
rules carrying the force of law. Under 42 U.S.C. § 405(a),
the Social Security Commissioner is granted “full power and
authority to make rules and regulations and to establish
procedures, not inconsistent with provisions of this
subchapter, which are necessary or appropriate to carry out
such provisions, and shall adopt reasonable and proper rules
and regulations[.]” See also 42 U.S.C. § 1383 (allowing the
Commissioner to define various statutory terms by
regulation); 42 U.S.C. § 902(a)(5) (granting the
Commissioner the authority to “carry out the functions of the
Administration” by rulemaking).

     But neither the SSA’s acquiescence ruling nor the SSA’s
POMS manual 5 carry the “force of law”; these agency
materials are issued without undergoing a process analogous
to legislative vetting, see Christensen, 529 U.S. at 587, and
they do not approximate formal rulemaking. See Sierra Club
v. Trump, 929 F.3d 670, 692 (9th Cir. 2019); see also Warre
v. Comm’r of Social Sec. Admin., 439 F.3d 1001, 1005 (9th
Cir. 2006) (“The POMS does not have the force of law, but
it is persuasive authority.”); Chavez v. Dep’t of Health and
Human Servs., 103 F.3d 849, 851 (9th Cir. 1996) (holding
that social security rulings “are interpretive rulings and do
not have the force of law”). For this reason, they are not
entitled to deference under Chevron.

     5
      The SSA’s interpretation also appears “loosely [ ] within the SSA’s
discussion of its implementing regulation for the uniformed services
exception.” Martin, 903 F.3d at 1160 & n.43 (citing 60 Fed. Reg.
56,511, 56,512 (Nov. 9, 1995)). The uniformed-services exception is
addressed in a single, brief sentence.
                       LARSON V. SAUL                        21

   An interpretation that does not carry the force of law,
however, may still be entitled to Skidmore deference as long
as it is not plainly erroneous or inconsistent with the
governing statute. See Chavez, 103 F.3d at 851. Here, the
acquiescence ruling states that the SSA

       interpret[s] the uniformed-services exception
       to the WEP to mean that only monthly
       payments based on military service are
       exempt from the WEP . . . . The legislative
       history of the [exception] explains that the
       purpose of the exception was to exempt
       military retired pay, based on noncovered
       [inactive duty training] military duty, from
       application of the WEP. The exception was
       not intended to exempt any pension based on
       civilian work from application of the WEP.

77 Fed. Reg. at 51,843. The acquiescence ruling is not
sufficiently detailed, careful, or imbued with the “power to
persuade,” such that it merits strong judicial deference. See
Skidmore, 323 U.S. at 140. SSA’s explanation for the ruling
is not particularly thorough, either: its explanation is limited
to a few sentences, see, e.g., Gen. Elec. Co. v. Gilbert,
429 U.S. 125, 142 (1976), and the rationale for not
exempting dual-status technicians’ CSRS pensions is based
entirely on a discussion of the legislative history, which—as
discussed—is itself unclear. See 77 Fed. Reg. at 51,843.
Nor are we convinced that the exception “was not intended
to exempt any pension based on civilian work from
application of the WEP,” id., simply because the history is
silent on this issue. The POMS is not much more helpful. It
limits the application of Petersen to the Eighth Circuit, but
does not contain any further justification for the SSA’s
decision to do so.
22                    LARSON V. SAUL

    Nonetheless,       the     Commissioner’s        preferred
interpretation of the uniformed-services provision is at least
a “permissible construction of the statute,” see United States
v. Home Concrete & Supply, LLC, 556 U.S. 478, 486–87
(2012), and the SSA’s longstanding, technical expertise in
administering the Social Security Act is owed deference. As
discussed, the provision can reasonably be interpreted in two
different ways: it can be understood as exempting from WEP
reduction all pension payments based on membership in the
armed forces, or as exempting such payments based on
service conducted as a member of the armed forces. The
SSA urges us to adopt the latter interpretation, and its
position is an acceptable reading of the text of the
uniformed-services provision.

    The provision concerns an “interstitial administrative
matter,” one in “which the agency’s expertise could have an
important role to play.” City of Arlington, Tex. v. FCC,
569 U.S. 290, 311 (2013) (Breyer, J., concurring in part and
in the judgment). Recognizing the Byzantine framework of
the Social Security Act and the intricacy involved in the
administration of social-security retirement benefits,
Congress chose to delegate broad authority to the SSA to
interpret its own statute and issue rules and regulations in
accordance with that statute. See Schweiker v. Gray
Panthers, 453 U.S. 34, 43 (1981). The complexity of the
Act and the need for agency expertise and guidance in its
interpretation warrant deference to the SSA in its reasonable
interpretive choices. See Aluminum Co. of Am. v. Cent.
Lincoln Peoples’ Util. Dist., 467 U.S. 380, 390 (1984).

    Although the uniformed-services exemption can be read
differently, the SSA’s construction “can be reasonable even
if another, equally permissible construction of the statute
could also be upheld.” Baldwin v. United States, 921 F.3d
                     LARSON V. SAUL                       23

836, 843 (9th Cir. 2019). For these reasons, we extend
deference to the SSA’s reading under Skidmore and hold that
the uniformed-services exemption does not apply to CSRS
payments received by dual-status technician retirees, such as
Larson.

   AFFIRMED.
