Court Opinion

ID: 4652418
Source: CourtListenerOpinion
Date Created: 2021-01-20 02:00:35.360829+00
Date Added: 2024-06-11T08:01:47.511815
License: Public Domain

(Slip Opinion)

 Military Support for Customs and Border Protection Along
    the Southern Border Under the Posse Comitatus Act
The Department of Defense’s proposed use of military personnel to provide limited
  assistance with respect to certain Customs and Border Protection inspection and
  observation functions along the southern border of the United States is permissible
  under the Posse Comitatus Act and applicable regulations.

                                                                    January 19, 2021

          MEMORANDUM OPINION FOR THE GENERAL COUNSEL
                   DEPARTMENT OF DEFENSE

   The Posse Comitatus Act, 18 U.S.C. § 1385, restricts the use of “any
part of the Army or the Air Force” in civilian law enforcement, unless
expressly authorized by law. Consistent with these restrictions, for many
years, the Department of Defense (“DoD”) has provided assistance to the
efforts by the Department of Homeland Security (“DHS”) to stem the
illegal flow of persons and contraband across the southern land border
between the United States and Mexico. This assistance is principally
authorized by chapter 15 of title 10 of the United States Code, 10 U.S.C.
§§ 271–284, which allows DoD to provide a number of different forms of
support to civilian law enforcement. Congress endorsed DoD’s ongoing
efforts in 2015 by providing that “[t]he Secretary of Defense may provide
assistance to United States Customs and Border Protection for purposes of
increasing ongoing efforts to secure the southern land border of the United
States.” National Defense Authorization Act for Fiscal Year 2016, Pub. L.
No. 114-92, § 1059, 129 Stat. 986‒87 (2015) (“FY 2016 NDAA”).
   In February 2020, DHS requested that DoD perform 26 specific duties
in support of U.S. Customs and Border Protection (“CBP”) operations at
the southern border for fiscal year 2021. See Memorandum for Oliver
Lewis, Captain, USN, Executive Secretary, Department of Defense, from
Juliana Blackwell, Acting Executive Secretary, Department of Homeland
Security, Re: Request for Extension of Department of Defense (DoD)
Assistance in Support of U.S. Customs and Border Protection’s (CBP)
Southwest Border (SWB) Security Mission Through Fiscal Year (FY) 2021
(Feb. 3, 2020). DoD approved support for 22 of these 26 duties, most of
which involved the kind of support that DoD already had been providing

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                       45 Op. O.L.C. __ (Jan. 19, 2021)

to DHS, such as motor-transport operations support and a crisis-response
force for certain urgent needs. See Memorandum for the Executive Secre-
tary, Department of Homeland Security, from David S. Soldow, Captain,
USN, Executive Secretary, Department of Defense, Re: Request for Ex-
tension of Department of Defense Assistance in Support of U.S. Customs
and Border Protection’s Southern Border Security Mission Through
Fiscal Year 2021 (June 23, 2020).
   DoD, however, held off on approving support for four duties pending
further consideration as to whether they would be consistent with the
Posse Comitatus Act and DoD regulations implementing chapter 15.
Those four duties concern rail-support, seal-check, port-of-entry-observer,
and checkpoint-observer functions. We understand that the rail-support
duty would have military personnel assist CBP personnel responsible
for inspecting unoccupied, unlocked vehicles being transported across
the southern border in bulk on rail cars. The seal-check duty would in-
volve visually verifying whether commercial cargo trucks and containers
have intact and unbroken seal tags, which CBP requires for trucks and
containers passing through ports of entry. The port-of-entry and check-
point observers would monitor the output of CBP’s electronic systems
that automatically collect and process data, such as license-plate infor-
mation, about individuals and vehicles passing through a port of entry or
U.S. Border Patrol checkpoint, and display an alert message if the system
identifies a concern.
   We conclude that neither the Posse Comitatus Act nor DoD’s regula-
tions prohibit the requested assistance. The rail-support and seal-check
duties would not violate the Posse Comitatus Act because they would not
involve military personnel subjecting civilians to military regulation,
directly or actively participating in civilian law enforcement activities, or
pervading the activities of civilian law enforcement. The port-of-entry and
checkpoint-observer duties would not violate the Posse Comitatus Act
because they would involve operating equipment and would not involve
direct participation in civilian law enforcement activities, as expressly
authorized by 10 U.S.C. § 274(c). All four duties would be similar to the
types of support that the courts and this Office’s precedents have held to
be consistent with the Posse Comitatus Act and DoD regulations, and that
the military is authorized to provide under chapter 15.

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   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
                                           I.

   The Posse Comitatus Act generally prohibits the use of the military to
engage in civilian law enforcement activities. At English common law,
the sheriff had the right to summon a body of available adults, the posse
comitatus, to assist in executing the laws or restoring civil order. See
Extraterritorial Effect of the Posse Comitatus Act, 13 Op. O.L.C. 321, 322
(1989). This practice continued in the United States, and in the Judiciary
Act of 1789, Congress vested the first federal law enforcement officers,
the U.S. Marshals, with the “power to command all necessary assistance
in the execution of [their] duty.” Act of Sept. 24, 1789, ch. 20, § 27,
1 Stat. 73, 87. That power remains with the U.S. Marshals Service, now
codified at 28 U.S.C. § 566(c).
   In enacting the Posse Comitatus Act in 1878, Congress sought to pre-
vent civilian law enforcement officials from generally relying upon the
U.S. Army to assist with the enforcement of the civilian laws. The statute
arose out of the objections of southern States to the use of the U.S. Army
in civilian law enforcement during the Reconstruction era. See Military
Use of Infrared Radars Technology to Assist Civilian Law Enforcement
Agencies, 15 Op. O.L.C. 36, 42 (1991) (“Military Use of Infrared Ra-
dars”); see Act of June 18, 1878, ch. 263, § 15, 20 Stat. 145, 152; 7 Cong.
Rec. 3845‒3852 (May 27, 1878); 7 Cong. Rec. 4239‒4248 (June 7, 1878).
But the statute’s restrictions are not limited to that historical episode and
instead reflect an American tradition of limiting direct military involve-
ment in civilian law enforcement. See, e.g., Laird v. Tatum, 408 U.S. 1, 15
(1972).
   In its current form, the statute provides that, except where “expressly
authorized by the Constitution or Act of Congress,” public officials may
not use “any part of the Army or the Air Force as a posse comitatus or
otherwise to execute the law.” 18 U.S.C. § 1385. 1 The prohibition thus
precludes “military personnel [from] applying force to the civilian com-
munity in the normal course of civil government” and prevents “actual or

   1 Although the Posse Comitatus Act applies only to the Army and the Air Force, DoD
regulations implementing similar restrictions apply to the Navy and the Marines. See DoD
Instruction 3025.21, ¶ 4.b, Defense Support of Civilian Law Enforcement Agencies (Feb.
27, 2013). The Secretary of Defense, however, is authorized to make exceptions on a
case-by-case basis. See id. encl. 3, ¶ 3.

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                       45 Op. O.L.C. __ (Jan. 19, 2021)

threatened coercion by persons subject to military discipline on behalf of
civil law enforcement officers.” Letter for Deanne Siemer, General Coun-
sel, Department of Defense, from Mary Lawton, Deputy Assistant Attor-
ney General, Office of Legal Counsel at 5 (Mar. 24, 1978) (“Lawton
Letter”).
   As relevant here, Congress has expressly authorized the military to
support civilian law enforcement under chapter 15. Among other things,
chapter 15 authorizes the military to provide to civilian law enforcement
information acquired in the normal course of military training or opera-
tions; equipment, training, and advice; and military personnel to maintain
and operate equipment. See 10 U.S.C. §§ 271–74. Chapter 15 also author-
izes military personnel to perform additional tasks in support of coun-
terdrug activities. See 10 U.S.C. § 284. But while granting DoD authority
to assist civilian law enforcement, Congress retained the core prohibition
of the Posse Comitatus Act by requiring that the Secretary of Defense
issue regulations “as may be necessary to ensure that any activity . . .
under this chapter does not include or permit the direct participation” of
a member of the military “in a search, seizure, arrest, or other similar
activity.” Id. § 275. The Secretary has implemented section 275 in DoD
Instruction 3025.21, Defense Support of Civilian Law Enforcement Agen-
cies (Feb. 27, 2013).
   The somewhat oblique prohibition under the Posse Comitatus Act
against using the military as “a posse comitatus or otherwise to execute
the law,” 18 U.S.C. § 1385, has led courts and this Office to employ
different tests against which to measure whether the activities in question
comply with this prohibition. See Memorandum for Jo Ann Harris, Assis-
tant Attorney General, Criminal Division, from Walter Dellinger, Assis-
tant Attorney General, Office of Legal Counsel, Re: Use of Military
Personnel for Monitoring Electronic Surveillance at 11 (Apr. 5, 1994)
(“Electronic Surveillance”) (“[T]he courts have employed three slightly
varying formulations of the test for determining whether military in-
volvement in civilian law enforcement has crossed the line separating
proper activity from violations of the PCA”); Riley v. Newton, 94 F.3d
632, 636 (11th Cir. 1996) (describing “three different tests”); United
States v. Yunis, 924 F.2d 1086, 1094 (D.C. Cir. 1991) (recognizing that
courts have employed “one of three tests”). We have recognized that an
action “does not violate the Posse Comitatus Act unless it actually regu-

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   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
lates, forbids, or compels some conduct on the part of those claiming
relief.” Electronic Surveillance at 10 (quoting Bissonette v. Haig, 776
F.2d 1384, 1390 (8th Cir. 1985), aff’d en banc, 800 F.2d 812 (8th Cir.
1986), aff’d, 485 U.S. 264 (1988)); see also Lawton Letter at 15‒16.
Under this test, courts consider whether a military activity “is that which
is regulatory, proscriptive, or compulsory in nature and causes the citizens
to be presently or prospectively subject to regulations, proscriptions, or
compulsions imposed by military authority.” United States v. McArthur,
419 F. Supp. 186, 194 (D.N.D. 1974), aff’d sub nom. United States v.
Casper, 541 F.2d 1275 (8th Cir. 1976) (per curiam).
   Courts have also employed a slightly different formulation: whether the
military is conducting law enforcement activities, rather than merely
supporting them, which is determined by whether the activities involve
“the direct active participation of federal military troops in law enforce-
ment activities.” United States v. Red Feather, 392 F. Supp. 916, 924
(D.S.D. 1975). As noted, this is the test that Congress directed the Secre-
tary of Defense to impose as a restriction on DoD’s support for civilian
law enforcement under chapter 15. See 10 U.S.C. § 275.
   Finally, in some cases, courts have employed a third test to ensure that
the military is not indirectly taking the lead in law enforcement activities,
even when it is not operating directly on civilians. These courts ask
whether the military activity in question “pervade[d] the activities of
civilian officials.” Hayes v. Hawes, 921 F.2d 100, 104 (7th Cir. 1990)
(quoting United States v. Bacon, 851 F.2d 1312, 1313 (11th Cir. 1988)
(per curiam)). In a recent case, the Ninth Circuit, sitting en banc, conclud-
ed that a Naval Criminal Investigative Service (“NCIS”) investigation into
child pornography on the Internet violated DoD regulations restricting law
enforcement activity by the Navy, because the NCIS investigation “per-
vaded the actions of civilian law enforcement.” United States v. Dreyer,
804 F.3d 1266, 1275 (9th Cir. 2015) (en banc). 2

   2 One issue in Dreyer was whether NCIS was targeting offenses by military personnel.

See 804 F.3d at 1276. It is well established that the Posse Comitatus Act does not restrict
the actions of military personnel “where the military has a legitimate interest for its own
proceedings or matters involving the internal administration of the military or the perfor-
mance of its proper functions.” Permissibility Under Posse Comitatus Act of Detail of
Defense Civilian Employee to the National Infrastructure Protection Center, 22 Op.
O.L.C. 103, 105‒06 (1998) (alteration and quotation marks omitted); see id. at 106

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                           45 Op. O.L.C. __ (Jan. 19, 2021)

   In our prior opinions, we have often applied the “direct active participa-
tion” test in considering whether the activities were consistent with the
restriction applicable to support provided under chapter 15. See, e.g.,
Memorandum for the Attorney General from Patrick F. Philbin, Deputy
Assistant Attorney General, Office of Legal Counsel, Re: Department of
Defense Assistance in an Federal Bureau of Investigation Domestic
Terrorism Investigation at 4 (Nov. 5, 2002) (“Domestic Terrorism”);
Military Use of Infrared Radars, 15 Op. O.L.C. at 38–39; Use of Depart-
ment of Defense Drug-Detecting Dogs to Aid in Civilian Law Enforce-
ment, 13 Op. O.L.C. 185, 186 (1989) (“DoD Drug-Detecting Dogs”). But
in opinions not involving chapter 15 support, we have generally followed
the lead of the courts of appeals by asking whether the military support
would be consistent with all three of the court-applied tests, without
worrying about whether they are all equally correct, or mutually exclu-
sive. See Permissibility Under Posse Comitatus Act of Detail of Defense
Civilian Employee to the National Infrastructure Protection Center, 22
Op. O.L.C. 103, 104 (1998) (“NIPC Detail ”) (asking whether the military
support violated any of these tests); Electronic Surveillance at 11 (same);
cf. Lawton Letter at 13 (concluding that the assistance in question did not
violate the Posse Comitatus Act because, under any of the formulations
the courts have employed, the assistance was “indirect and non-
authoritarian”).
   We understand from your request that DoD would assist DHS by using
National Guard members operating under federal command and control,
who would be considered as either part of the Army or Air Force while
operating in that status. See Use of the National Guard to Support Drug
Interdiction Efforts in the District of Columbia, 13 Op. O.L.C. 91, 92
(1989); Mueller v. City of Joliet, 943 F.3d 834, 837 (7th Cir. 2019). 3
Because those members would be subject to the Posse Comitatus Act, we
must first consider whether Congress has expressly authorized the mili-

(explaining that “[n]othing in the [Posse Comitatus Act] suggests that Congress intended
to circumscribe military participation in legitimately military matters”). Separately, the
Posse Comitatus Act does not apply outside United States territory. See Extraterritorial
Effect of the Posse Comitatus Act, 13 Op. O.L.C. at 344.
    3 By contrast, National Guard troops operating in militia status—that is, under state

command and control—are not subject to the Posse Comitatus Act. See Mueller, 943 F.3d
at 837; Clark v. United States, 322 F.3d 1358, 1367–68 (Fed. Cir. 2003).

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   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
tary to perform the four duties at issue. 4 Where Congress has not, we then
consider whether those tasks nevertheless would be consistent with the
Posse Comitatus Act.

                                           II.

   We begin with the rail-support and seal-check duties. Both tasks would
involve military personnel providing support to CBP in inspecting articles
coming across the border. Neither would involve the military engaging or
interacting directly with any civilians or assuming primary responsibility
for searching the vehicles, cargo trucks, or containers in question. Mili-
tary personnel would be under the direct supervision of CBP personnel,
would not be expected to have any contact with civilians, and would not
be expected to take custody of any evidence that might be used in any
subsequent legal proceeding, such as a criminal prosecution. Both military
and CBP personnel would receive training to ensure that they clearly
understand the scope of the approved activities of the military personnel.
   We understand that military personnel performing the rail-support duty
would assist CBP personnel in inspecting unoccupied, unlocked vehicles
being transported across the southern border in bulk on rail cars. This
inspection would occur in a secured and private rail yard, and vehicle
owners would have signed waivers authorizing the inspection. Military
personnel would open the doors, trunks, and hoods of unoccupied vehicles
to prepare them for CBP personnel’s subsequent inspection of the spaces
within the vehicles. Military personnel would not participate in that in-
spection. Military personnel would not be expected to make any observa-
tions as they open the vehicle doors, trunks, and hoods, but if they did
notice something suspicious, they would immediately notify CBP person-
nel. Military personnel would have no involvement in any subsequent
action.

   4 We do not believe that, under the facts presented, DoD’s assistance to DHS would be
expressly authorized by the Constitution. We have previously described the constitutional
exception to the PCA as applying to “any use of the military for constitutional purposes,”
including the deployment of “troops pursuant to a plenary constitutional authority.”
Memorandum for the Attorney General from Jay S. Bybee, Assistant Attorney General,
Office of Legal Counsel, Re: Determination of Enemy Belligerency and Military Deten-
tion at 9 (June 8, 2002). DoD’s assistance here to support DHS’s mission would not
involve the plenary constitutional authority of the President.

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                           45 Op. O.L.C. __ (Jan. 19, 2021)

   We understand that the seal-check duty would involve similar support
to CBP personnel. Military personnel would visually verify whether
commercial cargo trucks and containers have intact and unbroken seal
tags, which are required for the trucks and containers as they pass through
ports of entry. This activity would take place at locations secured and
controlled by CBP. Seal tags are located in plain view on the outside of
the trucks and containers. In some cases, the cargo truck driver may be in
the cabin of the truck while military personnel check whether the truck’s
seal tag is intact, but the seal tag is located at the rear of the truck and
military personnel are not expected to have any contact with the driver. If
military personnel notice a discrepancy in a seal tag, then they would
immediately notify CBP personnel and would not participate in any
subsequent inspection performed by CBP personnel.

                                          A.

   We first consider whether these tasks are expressly authorized under
chapter 15 or under the FY 2016 NDAA. We think that the chapter 15
question is straightforward, because neither the rail-support or seal-check
duties fit within the tasks authorized under chapter 15. Sections 271 to
274 authorize DoD to support civilian law enforcement agencies by
providing information, military equipment and facilities, training and
advising, or the maintenance and operation of equipment. See 10 U.S.C.
§ 271–74. None applies here. Section 284(b)(6) likewise authorizes DoD
to assist through the “detection, monitoring, and communication” of air,
sea, and surface traffic within designated parameters of the U.S. borders,
but those provisions do not speak to the inspection of goods. Likewise,
we do not believe that any of the other activities authorized by section
284(b) would readily apply to these tasks.
   Whether section 1059 expressly authorizes the rail-support or seal-
check duties for purposes of the Posse Comitatus Act, however, is a closer
question. As relevant here, section 1059(a) states that “[t]he Secretary of
Defense may provide assistance to United States Customs and Border
Protection for purposes of increasing ongoing efforts to secure the south-
ern land border of the United States.” FY 2016 NDAA § 1059(a). 5 The
section continues:

    5 Section 1059 was enacted as part of the FY 2016 NDAA, but the section has no expi-

ration date and remains in effect. See, e.g., United States v. Hernandez-Garcia, No. 19-

                                           8
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
      The assistance provided under subsection (a) may include the fol-
      lowing:
           (1) Deployment of members and units of the regular and re-
        serve components of the Armed Forces to the southern land bor-
        der of the United States.
           (2) Deployment of manned aircraft, unmanned aerial surveil-
        lance systems, and ground-based surveillance systems to support
        continuous surveillance of the southern land border of the United
        States.
           (3) Intelligence analysis support.
Id. § 1059(c). The rail-support and seal-check duties do not fall into any
of the categories of activities specifically mentioned in section 1059(c)(2)
and (c)(3): They involve neither the “[d]eployment” of the aircraft and
surveillance equipment nor “[i]ntelligence analysis support.” The duties
could perhaps be viewed as falling within section 1059(c)(1), which
permits the general “[d]eployment” of military personnel “to the southern
land border” without specifying what missions such personnel would
perform.
   In addition, the categories in subsection (c) are not exclusive. The stat-
ute makes clear that the assistance “may include the following.” See
Burgess v. United States, 553 U.S. 124, 131 n.3 (2008) (“[T]he word
‘includes’ is usually a term of enlargement, and not of limitation.” (quot-
ing 2A Norman J. Singer & J.D. Shambie Singer, Sutherland on Statutory
Construction § 47:7, at 305 (7th ed. 2007)). So we must also consider
whether the rail-support and seal-check duties fall within the statute’s
authorization for general “assistance” to CBP for “purposes of increasing
ongoing efforts to secure the southern land border” under section 1059(a).

CR-4373-GPC, 2020 WL 1083427, at *2 (S.D. Cal. Mar. 6, 2020) (“[T]he provision lacks
any language expressly limiting its operative terms to fiscal year 2016.”); United States v.
Rios-Montano, 438 F. Supp. 3d 1149, 1151–52 (S.D. Cal. 2020) (rejecting the argument
that section 1059’s “legal effect lapsed with fiscal year 2016” because the section “pro-
vides an unrestrained grant of authority” and “contains no sunset provision”); see general-
ly Memorandum for Mary De Rosa, Legal Adviser, National Security Council, from
David J. Barron, Acting Assistant Attorney General, Re: Engagement with the Interna-
tional Criminal Court at 3 (Jan. 15, 2010) (noting that the “presumption against perma-
nency” does not “automatically apply” to authorization acts (quotation marks omitted)).

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                        45 Op. O.L.C. __ (Jan. 19, 2021)

   The question then is whether either of these sections constitute express
authorization for purposes of the Posse Comitatus Act. Both section
1059(a) and section 1059(c)(1) no doubt generally authorize deploying
military personnel to the southern border to provide “assistance” to CBP
in support of “ongoing efforts to secure the southern land border.” But it
does not follow that this authorization necessarily “expressly” authorizes
actions that would otherwise violate the Posse Comitatus Act. 18 U.S.C.
§ 1385. In 1878, as now, “expressly” means “[i]n an express manner,” “in
direct terms,” or “plainly.” Noah Webster, A Dictionary of the English
Language 156 (1878 ed.); Henry Campbell Black, Dictionary of Law
Containing Definitions of the Terms and Phrases of American and Eng-
lish Jurisprudence, Ancient and Modern 462 (1891) (defining “express”
to mean “[m]ade known distinctly and explicitly, and not left to inference
or implication”); Webster’s (Third) New International Dictionary of the
English Language 803 (1993) (defining “expressly” to mean “in direct or
unmistakable terms.”).
   Thus, for a statute to authorize a military activity expressly for pur-
poses of the Posse Comitatus Act, we think that it must be clear that
Congress has approved that activity without regard to the restrictions on
using the military “as a posse comitatus or otherwise to execute the
laws.” 18 U.S.C. § 1385; see Dorsey v. United States, 567 U.S. 260, 273–
75 (2012) (holding that statutory requirement that the “repeal of any
statute shall not have the effect to release or extinguish any penalty,
forfeiture, or liability incurred under such statute, unless the repealing Act
shall so expressly provide,” 1 U.S.C. § 109, is satisfied where the “plain
import” or “fair implication” of the repealing Act is that it should apply to
pre-Act offenders). We do not think that a general authorization of “assis-
tance” necessarily means that the restrictions of the Posse Comitatus Act
fall away.
   The generic authorization in section 1059(a) and (c)(1) to “[d]eploy”
military personnel “to the southern land border of the United States” for
“assistance” to CBP in “ongoing efforts” does not reflect that kind of
clear approval. To the contrary, we think that section 1059 points not to
new forms of support DoD may provide, but rather toward the types of
assistance that DoD had already been providing to CBP as part of “ongo-
ing efforts,” which include the types of activities specifically mentioned
in section 1059(c)(2) and (c)(3). A contrary reading would dramatically
change DoD’s assistance to these “ongoing efforts,” authorizing DoD to
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   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
perform functions not traditionally done at the southern border, including
through “direct participation” by the military “in a search, seizure, arrest,
or other similar activity.” 10 U.S.C. § 275; see also Memorandum for
Jamie Gorelick, Deputy Attorney General, from Walter Dellinger, Assis-
tant Attorney General, Office of Legal Counsel, Re: Use of Military to
Enforce Immigration Laws at 2 (May 10, 1994) (“Immigration Laws”)
(recognizing that the “direct use of the military to detain or arrest suspect
aliens would violate” the Posse Comitatus Act “unless otherwise author-
ized by law”). We think it quite unlikely that Congress would have so
significantly changed DoD’s mission at the border by generally authoriz-
ing the “deployment” of military personnel to provide “assistance.”
   Where Congress has affirmatively authorized DoD to provide assis-
tance to law enforcement in other contexts, it has often included re-
strictions on the military’s “direct participation” in encounters with
civilians. In fact, in another provision of the FY 2016 NDAA, Congress
authorized the military to provide “assistance” to the Department of
Justice in its efforts to investigate domestic bombings of places of public
use or of Government facilities. FY 2016 NDAA § 1082(a), 129 Stat. at
1003–04 (codifying 10 U.S.C. § 383, now 10 U.S.C. § 283). In so doing,
Congress took care to specify that military personnel were not authorized
to engage in “arrest[s]”; any “direct participation in conducting a search
for or seizure of evidence”; or any “direct participation in the collection
of intelligence for law enforcement purposes,” save in narrowly delineat-
ed circumstances. Id. (codifying 10 U.S.C. § 383(c)(2), now 10 U.S.C.
§ 283(c)(2)); see also 10 U.S.C. § 282(c)(2)(B) (providing similar limited
authority for military personnel to engage in searches and seizures in
investigating emergency situations involving weapons of mass destruc-
tions).
   Congress provided no such limitation in authorizing “assistance” under
section 1059. One could perhaps infer from the absence of such language
that Congress intended to authorize DoD to provide assistance to CBP in a
manner that did not restrict “direct participation” in arrests, searches, and
seizures. See Russello v. United States, 464 U.S. 16, 23 (1983) (“Where
Congress includes particular language in one section of a statute, but
omits it in another section of the same Act, it is generally presumed that
Congress acts intentionally and purposely in the disparate inclusion or
exclusion.” (quotation marks and brackets omitted)). But we think that the

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                           45 Op. O.L.C. __ (Jan. 19, 2021)

more likely inference is that Congress sought to authorize the kinds of
“ongoing” assistance that DoD had been providing under chapter 15,
consistent with the existing statutory restriction on “direct participation”
required by 10 U.S.C. § 275. 6 At a minimum, with two plausible inter-
pretations available, we cannot say that Congress expressly authorized
the support to proceed without regard to the restrictions of the Posse
Comitatus Act.
   Elsewhere, when Congress has authorized the military to engage in ci-
vilian law enforcement activities, it has explicitly stated that the Posse
Comitatus Act is inapplicable to those activities, see, e.g., 5 U.S.C. app. 3,
§ 8(g) (“The provisions of section 1385 of title 18, United States Code,
shall not apply to audits and investigations conducted by, under the direc-
tion of, or at the request of the Inspector General of the Department of
Defense to carry out the purposes of this Act.”); 18 U.S.C. § 831(f )(1)
(stating that DoD may provide specified assistance to the Attorney Gen-
eral “[n]otwithstanding section 1385 of this title” if certain conditions are
met), or authorized the military to engage in activities that plainly involve
coercive action against civilians, see, e.g., 10 U.S.C. § 251 (authorizing
the military, under certain circumstances, to “suppress . . . insurrec-
tion[s]”); id. § 252 (authorizing the military to “enforce the laws of the
United States” and to “suppress . . . rebellion[s]”); id. § 253 (authorizing
the military to take needed “measures . . . to suppress . . . any insurrec-
tion, domestic violence, unlawful combination, or conspiracy”); 18 U.S.C.
§ 112(f ) (authorizing the Attorney General to seek the assistance of,

   6 This interpretation is consistent with the section 1059’s legislative history, which

reflects an intent to authorize “the ongoing efforts by [DoD] to provide additional assis-
tance to secure the southern land border of the United States”—assistance that DoD
provided consistent with the Posse Comitatus Act—and desire that DoD “continue these
efforts and coordinate with the Secretary of Homeland Security to identify opportunities
to provide additional support.” Sen. Rep. No. 114-49, at 206 (2015) (emphases added);
see also National Defense Authorization Act for Fiscal Year 2016: Legislative Text and
Joint Explanatory Statement 740 (Comm. Print Nov. 2015) (noting that section 1059
“would authorize the Secretary of Defense . . . to provide assistance to [CBP] for the
purpose of increasing the ongoing efforts to secure the southern land border of the United
States” (emphasis added)). We have not located any legislative history suggesting that
Congress intended that military personnel deployed to the border to provide “assistance”
to CBP under section 1059 could depart from the sort of assistance the military had
previously provided to civilian law enforcement consistent with the Posse Comitatus Act
and DoD’s regulations.

                                           12
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
among other agencies “the Army, Navy, and Air Force” in enforcing the
criminal prohibition on harming foreign dignitaries); id. § 1751(i) (author-
izing the Attorney General to seek the assistance of, among other agencies
“the Army, Navy, and Air Force” in investigating the criminal prohibition
on murdering or assaulting the President or presidential staff ). See gener-
ally Extraterritorial Effect of the Posse Comitatus Act, 13 Op. O.L.C. at
340 (discussing 21 U.S.C. § 873(b), which authorizes the Attorney Gen-
eral to request military assistance to enforce the Controlled Substances
Act).
   We think that these specific authorizations in the U.S. Code for the mil-
itary to provide particular support reinforce that the more general authori-
zation of assistance in section 1059 should not be read to authorize ac-
tions without regard to the limitations of the Posse Comitatus Act. As the
Court has recognized, “the meaning of one statute may be affected by
other Acts, particularly where Congress has spoken subsequently and
more specifically to the topic at hand.” Food & Drug Admin. v. Brown &
Williamson Tobacco Corp., 529 U.S. 120, 133 (2000). In addition, specif-
ic statutory provisions inform the meaning of more general ones, and this
canon “has full application . . . to statutes . . . in which a general authori-
zation and a more limited, specific authorization exist side-by-side.”
RadLAX Gateway Hotel, LLC v. Amalgamated Bank, 566 U.S. 639, 645
(2012). The contrast between the generality of section 1059 and the speci-
ficity of these other provisions suggest that Congress did not intend sec-
tion 1059(a) and (c)(1) to authorize the “deployment” of military person-
nel to provide “assistance” to CBP without regard to whether such as-
sistance would otherwise violate the Posse Comitatus Act.
   This interpretation is consistent with the Office’s prior caution in read-
ing generally worded statutes to authorize the military to engage in coer-
cive civilian law enforcement activities. In 1994, this Office concluded
that the Attorney General’s authority to delegate immigration law en-
forcement functions to “any employee of the United States” did not clear-
ly authorize the Attorney General to delegate such authority to military
personnel to engage in immigration-enforcement activities that would
otherwise violate the Posse Comitatus Act. 7 See Immigration Laws at 9–

   7 The authority was then vested in the Attorney General. See 8 U.S.C. § 1103(a)

(1994). The Homeland Security Act of 2002 transferred most immigration-enforcement
functions to the Secretary of Homeland Security. See Homeland Security Act of 2002,

                                        13
                            45 Op. O.L.C. __ (Jan. 19, 2021)

12. We explained that where a determination that a statute constitutes
express authority for purposes of the Posse Comitatus Act “would repre-
sent a sharp departure from the traditional restrictions embodied” in the
statute, the determination “should rest on a well-founded conviction that
Congress intended such a result” because “it cannot be assumed that
Congress would approve such a major change in the military’s permissi-
ble law enforcement role without providing some specific indication that
it was doing so.” Id. at 12. The same year, we concluded that general
language in the Electronic Communications Privacy Act of 1986 authoriz-
ing “government personnel” to assist in electronic surveillance, see 18
U.S.C. § 2518(5), was insufficiently clear to authorize expressly military
personnel to engage in surveillance that would otherwise violate the Posse
Comitatus Act. See Electronic Surveillance at 4‒6. These precedents
suggest that the similarly general authorization in section 1059 does not
authorize coercive military participation in civilian law enforcement
activities with the requisite clarity.
   This conclusion also accords with judicial opinions addressing whether
an activity is expressly authorized for purposes of the Posse Comitatus
Act. Courts have found such express authority when the statute specifical-
ly refers to the Posse Comitatus Act. See, e.g., United States v. Stouder,
724 F. Supp. 951, 954 (M.D. Ga. 1989) (“Congress specified in § 8(g) of
the Inspector General Act of 1978 that . . . ‘[t]he provisions of section
1385 of title 18, United States Code . . . shall not apply to audits and
investigations conducted by . . . the Inspector General of the Department
of Defense.’”). They have reached the same conclusion when the statute
authorizes the military to engage in a particular activity with such speci-
ficity that Congress clearly approved the particular use of the military. 8

Pub. L. No. 107-296, § 1102(2)(A), 116 Stat. 2135, 2273 (2002), as amended by Consoli-
dated Appropriations Resolution, Pub. L. No. 108-7, div. L, § 105(a)(1), 107 Stat. 11, 531
(2003).
   8 See, e.g., Gilbert v. United States, 165 F.3d 470, 473‒74 (6th Cir. 1999) (noting that

32 U.S.C. § 112(b) authorizes the National Guard, while not in federal service, to be used
for the “purpose of carrying out drug interdiction and counter-drug activities”); United
States v. Al-Talib, 55 F.3d 923, 930 (4th Cir. 1995) (“This DEA airlift was specifically
authorized by § 1004 of the National Defense Authorization Act for Fiscal Year 1991
(‘NDAA’), which allows military ‘transportation of supplies and equipment for the
purpose of facilitating counter-drug activities.’”); United States v. Allred, 867 F.2d 856,

                                           14
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
   At the same time, we have identified several decisions that have read
somewhat general statutes as constituting express authorization under the
Posse Comitatus Act. Of note, two district court judges have suggested,
albeit with little analysis, that section 1059 does constitute express author-
ization under the Posse Comitatus Act. See United States v. Hernandez-
Garcia, No. 19-CR-4373-GPC, 2020 WL 1083427, at *3 (S.D. Cal.
Mar. 6, 2020) (Curiel, J.) (“[T[he Court finds that the 2016 NDAA unam-
biguously authorized the participation of DoD personnel at issue here,
namely, their observation of someone alleged to be Mr. Hernandez-Garcia
through a scope, and their subsequent communication with BPA Allen-
Limon as to that person’s location.”); United States v. Cardenas-Tovar,
No. 19-CR-04370-BTM, 2020 WL 905634, at *3 (Feb. 25, 2020) (Mos-
kowitz, J.) (“Even assuming arguendo that the Marines’ involvement rose
to the level of direct involvement, however, such involvement appears to
have been ‘otherwise authorized by law’ pursuant to Section 1059 of the
National Defense Authorization Act for Fiscal Year 2016.”); United
States v. Rios-Montano, 438 F. Supp. 3d 1149, 1151, 1054‒55 (S.D. Cal.
2020) (Curiel, J.) (agreeing that section 1059 “‘authorize[s] by law’ the
Marine Corps’ conduct on the United States’ southern border with Mexi-
co” (alteration in original)). We believe that these decisions are correct
insofar as these cases involved military surveillance activities that were
specifically and expressly authorized by section 1059(c)(2). But we would
not read these decisions as suggesting that section 1059(a) and (c)(1)
expressly authorize the deployment of military personnel to provide
assistance to CBP without regard whether to such assistance would oth-
erwise conflict with the Posse Comitatus Act.
   Two other courts have similarly read general statutes to constitute ex-
press authorization of certain activities for purposes of the Posse Comita-
tus Act. See United States v. Allred, 867 F.2d 856, 871 (5th Cir. 1989)
(suggesting, in dictum, that the Attorney General’s authority to appoint
Special Assistant United States Attorneys constitutes an express auth-
orization for purposes of the Posse Comitatus Act); Red Feather, 392
F. Supp. at 923 (“The Economy Act, 31 U.S.C. § 686, expressly authoriz-
es any executive department or independent establishment of the govern-
ment, or any bureau or office thereof, to place orders with any other such

871 (5th Cir. 1989) (relying on 10 U.S.C. § 806(d)(1) in holding that military lawyers are
statutorily authorized to represent the United States in criminal cases).

                                           15
                            45 Op. O.L.C. __ (Jan. 19, 2021)

department, establishment, bureau, or office, for materials, supplies, or
equipment.” (quotation marks omitted)). We think that the better reading
of the decisions in these cases, if not their reasoning, is that the pertinent
activities, such as furnishing materials or supplies or the use of a commis-
sioned officer of the Judge Advocate General’s Corps (“JAGC”) as a
special assistant to a United States Attorney, would generally not have
violated the Posse Comitatus Act even without express authorization.
See Bissonette, 776 F.2d at 1390 (“[T]he mere furnishing of materials and
supplies cannot violate the [Posse Comitatus Act].”); Assignment of Army
Lawyers to the Department of Justice, 10 Op. O.L.C. 115, 116 (1986)
(“The Department may use JAGC lawyers to assist in preparing cases and
in performing a number of other duties in connection with civil and crimi-
nal litigation under our responsibility, without raising issues under the
Posse Comitatus Act.”). 9 Neither Allred nor Red Feather considered
section 1059 or, of course, whether it constitutes express authorization
under the Posse Comitatus Act.
   Finally, our conclusion that section 1059(a) and (c)(1) does not ex-
pressly authorize the military to engage in activities without regard to the
restrictions of the Posse Comitatus Act is consistent with DoD’s practices
since 2016. For many years now, DoD has deployed military personnel to
the southern border to assist DHS, but has not used such personnel to
conduct coercive immigration-enforcement activities. This Office, too,
has regularly provided advice to DoD concerning the legal restrictions on
the use of military in its ongoing support for DHS at the southern border,
including with respect to the national emergency declared by the President
on February 15, 2019, see Declaring a National Emergency Concerning
the Southern Border of the United States, Proclamation No. 9844, 84 Fed.
Reg. 4949 (Feb. 15, 2019). We have advised, for example, regarding
whether certain military support provided to DHS is authorized by chapter
15, whether military personnel could engage in coercive civilian law
enforcement activities in protecting ports of entry and other federal prop-

   9 The JAGC opinion also stated that “questions under the Posse Comitatus Act may be

raised if military lawyers perform prosecutorial functions involving direct contact with
civilians, unless such military lawyers are detailed to the Department on a full-time basis
and operate under the supervision of departmental personnel.” Assignment of Army
Lawyers to the Department of Justice, 10 Op. O.L.C. at 116. The extent to which these
“questions” might have been implicated by the facts in Allred is unclear, and in any event
we need not address them here.

                                           16
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
erty near the southern border, and whether the Insurrection Act could be
invoked to stem the flow of illegal aliens across the southern border. At
no point during these discussions has DoD or this Office treated section
1059(a) and (c)(1) as providing express authorization that would effec-
tively moot any further consideration concerning the restrictions imposed
by the Posse Comitatus Act.

                                       B.

   Because DoD’s activities at the border remain subject to the Posse
Comitatus Act, we must consider whether the rail-support and seal-check
duties are consistent with the statute’s restrictions. In accordance with the
approach taken in our prior opinions, we review these activities based
upon each of the three tests that courts have used in evaluating military
activities for compliance with the Posse Comitatus Act. We conclude that
DoD’s limited support for CBP inspections does not involve military
personnel in the kind of coercive regulatory activity, direct participation
in civilian law enforcement, or pervasive conduct that is prohibited by the
Posse Comitatus Act absent express authorization.

                                       1.

   To start, we do not think that the rail-support and seal-check duties
would subject any civilians to military regulation, proscription, or com-
pulsion. NIPC Detail, 22 Op. O.L.C. at 105. Courts have explained that
“[a] power regulatory in nature is one which controls or directs,” “[a]
power proscriptive in nature is one that prohibits or condemns,” and “[a]
power compulsory in nature is one that exerts some coercive force.”
United States v. Yunis, 681 F. Supp. 891, 895‒96 (D.D.C. 1988), aff’d 924
F.2d 1086 (D.C. Cir. 1991); United States v. Gerena, 649 F. Supp. 1179,
1182‒83 (D. Conn. 1986) (same).
   The Eighth Circuit considered when military activities subject civilians
to military regulation, proscription, or compulsion in Bissonette v. Haig.
That case was one of several to arise from the U.S. military’s involvement
in a 1973 occupation by protesters of the town of Wounded Knee, South
Dakota. The plaintiffs alleged that military personnel “maintained or
caused to be maintained roadblocks and armed patrols constituting an
armed perimeter around the village of Wounded Knee,” which “seized,

                                       17
                        45 Op. O.L.C. __ (Jan. 19, 2021)

confined, and made prisoners [of plaintiffs] against their will,” and they
also alleged that “they were searched and subjected to surveillance against
their will by aerial photographic and visual search and surveillance.” 776
F.2d at 1390–91. As to the allegations that troops had engaged in aerial
surveillance, the court held that “that this sort of activity does not violate
the Posse Comitatus Act.” Id. at 1391. But the court held that the mili-
tary’s alleged activities in seizing individuals while setting up a roadblock
sufficiently stated a claim that the troops had “in violation of the Posse
Comitatus Act” engaged in activities that “were ‘regulatory, proscriptive,
or compulsory’” because they involved a claim that military personnel
“directly restrained plaintiffs’ freedom of movement.” Id.
   Here, military personnel performing the rail-support and seal-check du-
ties are not expected to have any contact with civilians—much less to
control, direct, coerce, or otherwise regulate them. See United States v.
Bacon, 851 F.2d 1312, 1313 ‒14 (11th Cir. 1988) (per curiam) (Army
agent’s undercover role in state drug investigation did not subject citizen-
ry to regulatory exercise of military power, and therefore did not violate
the Posse Comitatus Act); United States v. Moraga, No. 01-964, 2002 WL
35649965, at *10 (D.N.M. 2002) (use of air force dog and handler did not
“compel the Defendant to do anything or forbid the Defendant from doing
anything”); Electronic Surveillance at 11 (“Mere assistance by military
personnel in the monitoring of court-authorized electronic surveillance by
civilian authorities . . . is neither regulatory nor proscriptive, nor is it a
compulsory application of military power”). Military personnel would
provide support to CBP personnel by engaging in plain-view inspections
of property and the fairly ministerial tasks of opening unoccupied vehi-
cles. There is no sense in which such actions would subject civilians to
military regulation, proscription, or compulsion.

                                      2.

   We next consider the “direct active participation” test, which asks
whether military personnel have “direct active” involvement in law en-
forcement activities, or instead are playing a “passive role in civilian law
enforcement activities.” Red Feather, 392 F. Supp. at 924; see NIPC
Detail, 22 Op. O.L.C. at 105; Domestic Terrorism at 4; Electronic Sur-
veillance at 8. This test “permits a broad degree of cooperation between
the military and civilian law enforcement.” NIPC Detail, 22 Op. O.L.C. at

                                      18
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
105. “Activities which constitute an active role in direct law enforcement
are: arrest; seizure of evidence; search of a person; search of a building;
investigation of crime; interviewing witnesses; pursuit of an escaped
civilian prisoner; search of an area for a suspect and other like activities.”
Red Feather, 392 F. Supp. at 925; see also Immigration Laws at 2. By
contrast,
        [a]ctivities which constitute a passive role which might indirectly aid
        law enforcement are: mere presence of military personnel under or-
        ders to report on the necessity for military intervention; preparation
        of contingency plans to be used if military intervention is ordered;
        advice or recommendations given to civilian law enforcement offic-
        ers by military personnel on tactics or logistics; presence of military
        personnel to deliver military materiel, equipment or supplies, to train
        local law enforcement officials on the proper use and care of such
        material or equipment, and to maintain such materiel or equipment;
        aerial photographic reconnaissance flights and other like activities.
Red Feather, 392 F. Supp. at 925 (emphasis omitted); see also Yunis, 924
F.2d at 1094.
   We believe that the military’s provision of personnel to perform the
rail-support and seal-check duties is permissible indirect, passive assis-
tance under this framework. These duties would not require military
personnel to perform any traditional law enforcement task, such as the
arrest, seizure, or search of a person. There is a sense in which these
duties may involve military personnel “searching” commercial cargo
trucks and containers and vehicle compartments, at least to a small de-
gree. 10 But our precedents make clear that not every activity that could be
described as a “search,” even if it is a “search” for purposes of the Fourth
Amendment, constitutes direct participation in civilian law enforcement.

   10 The opening of a closed vehicle would likely constitute a search under the Fourth
Amendment. See United States v. Jones, 565 U.S. 400, 406 n.3 (2012) (“Where, as here,
the Government obtains information by physically intruding on a constitutionally protect-
ed area, such a search has undoubtedly occurred.”). A plain-view search, however, of the
seals on a cargo container would not. See id. at 412 (“This Court has to date not deviated
from the understanding that mere visual observation does not constitute a search.”); New
York v. Class, 475 U.S. 106, 114 (1986) (“The exterior of a car, of course, is thrust into
the public eye, and thus to examine it does not constitute a ‘search.’”).

                                           19
                            45 Op. O.L.C. __ (Jan. 19, 2021)

   In Military Use of Infrared Radars, for instance, we advised that mili-
tary personnel do not directly participate in civilian law enforcement
merely by providing aerial reconnaissance using Forward Looking Infra-
red Radars (“FLIR”) technology to assist in identifying structures sus-
pected of illegal drug production. See 15 Op. O.L.C. at 36–38. We as-
sumed without deciding that FLIR surveillance might be a “search” for
purposes of the Fourth Amendment but did not find that fact dispositive. 11
Instead, we concluded that “searches” constitute direct participation “at
most” when they involve “physical contact with civilians or their proper-
ty,” and even then “perhaps only” when the searches involve “physical
contact that [is] likely to result in a direct confrontation between military
personnel and civilians.” Id. at 39–40; see also Domestic Terrorism at 4
(same); Military Use of Infrared Radars, 15 Op. O.L.C. at 44 (reading
the direct-participation restriction “to prohibit only activity that entailed
direct, physical confrontation between military personnel and civilians”).
And the courts too agree that surveillance operations, such as aerial re-
connaissance, in support of civilian law enforcement constitute permissi-
ble indirect assistance. See United States v. Hartley, 796 F.2d 112, 114
(5th Cir. 1986) (“[I]n examining allegations that military involvement in
civilian law enforcement violated the Posse Comitatus Act, courts have
noted that ‘aerial photographic reconnaissance flights and other like
activities’ do not reflect direct military involvement violative of the Posse
Comitatus Act.” (quoting Red Feather, 392 F. Supp. at 925, and collecting
cases)); Bissonette, 776 F.2d at 1391 (“[P]laintiffs charge that they were
searched and subjected to surveillance against their will by aerial photo-
graphic and visual search and surveillance. As we have already noted . . .
this sort of activity does not violate the Posse Comitatus Act.”). 12

   11  See Military Use of Infrared Radars, 15 Op. O.L.C. at 48; see generally Kyllo v.
United States, 533 U.S. 27, 34 (2001) (“We think that obtaining by sense-enhancing
technology any information regarding the interior of the home that could not otherwise
have been obtained without physical intrusion into a constitutionally protected area
constitutes a search—at least where (as here) the technology in question is not in general
public use.” (citation and quotation marks omitted)).
    12 In United States v. Johnson, 410 F.3d 137, 147 (4th Cir. 2005), the Fourth Circuit

stated that “[a] blood test constitutes a search under the Fourth Amendment . . . and thus
falls under the rubric of law enforcement activities” requiring express congressional
authorization. Unlike the rail-support and seal-check duties, the conduct of a blood test is
an investigative activity and puts military officers within the chain of custody of evi-

                                            20
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
   We reached similar conclusions in opinions approving DoD support for
civilian law enforcement by supplying drug-detecting dogs with military
handlers. We agreed that DoD may provide this support “to identify
packages containing illegal narcotics” because “the proposed use of the
dogs and their handlers will not involve confrontation with civilians.” Use
of Navy Drug-Detecting Dogs by Civilian Postal Inspectors, 13 Op.
O.L.C. 312, 316 (1989); see also DoD Drug-Detecting Dogs, 13 Op.
O.L.C. at 186 (“[W]e believe that drug-detecting dogs may be used in
searches of packages and places in the absence of persons with whom a
confrontation may arise, as long as the actual seizure is made by civilian
law enforcement personnel.”). This was true notwithstanding the likeli-
hood of physical contact with civilian property. See generally United
States v. Olivera-Mendez, 484 F.3d 505, 511 (8th Cir. 2007) (“Ajax
jumped and placed his front paws on the body of the car in several places
during a walk-around sniff that took less than one minute.”).
   Courts have also held that military activities constituted permissible
indirect support even where those activities involved some degree of
physical contact with civilian property. In United States v. Khan, 35 F.3d
426 (9th Cir. 1994), the court held that Navy “logistical support and
backup security” for a Coast Guard operation to interdict a suspected
drug-smuggling ship constituted permissible indirect assistance notwith-
standing the fact that Navy personnel actually boarded the ship. Id. at
431‒32. The court explained that “Navy personnel on board the [ship] had
acted under the command of the Coast Guard, and that only the Coast
Guard had searched the ship and arrested the crew.” Id. at 432. Similarly,
the court in United States v. Klimavicius-Viloria, 144 F.3d 1249 (9th Cir.
1998), concluded that similar Navy assistance was permissible indirect
assistance to civilian law enforcement, even though, in addition to board-
ing the ship, “Navy engineers in the present case moved the fluids among
the fifteen tanks” in order to facilitate a search of the tanks. Id. at 1259. 13

dence. We do not read Johnson as holding that every military activity that might consti-
tute a “search” for purposes of the Fourth Amendment necessarily constitutes the direct
active use of military personnel in civilian law enforcement for purposes of the Posse
Comitatus Act.
   13 In Johnson, military personnel performed a blood test that “would yield the primary

evidence of guilt of a DUI offense and, should the driver not plead guilty and go to trial,
the serviceman who performed the test likely would be called to testify.” 410 F.3d at 148.
By contrast, military personnel performing the rail-support and seal-check duties would

                                           21
                         45 Op. O.L.C. __ (Jan. 19, 2021)

   We think that both the rail-support and seal-check duties are plainly
permissible under these precedents. The seal-check duty neither “in-
volv[es] physical contact with civilians or their property” nor is “likely to
result in a direct confrontation between military personnel and civilians.”
Military Use of Infrared Radars, 15 Op. O.L.C. at 39–40. Military per-
sonnel would merely observe the exteriors of cargo trucks and containers,
and would have no physical contact with that property. With respect to the
rail-support duty, military personnel would prepare the vehicles for in-
spection by CBP by opening vehicle doors, trunks, and hoods, but such
cursory and incidental physical contact does not amount to direct partici-
pation. The military personnel’s assistance to CBP is not likely to result in
any interactions with civilians, since the vehicles would be unmanned and
in a restricted rail yard. And if military personnel notice anything suspi-
cious, they would immediately notify CBP personnel and not participate
in any resulting law enforcement activities.
   Because the rail-support and seal-check duties would not require mili-
tary personnel to directly participate in traditional law enforcement activi-
ties, such as a search, seizure, or arrest, as those terms are understood in
common parlance, and would not risk a confrontation with civilians, we
do not believe that either duty would involve the direct active participa-
tion of military personnel in civilian law enforcement.

                                        3.

   Finally, the rail-support and seal-check duties in no way involve the
activities of military personnel “pervad[ing] the activities of civilian law
enforcement.” NIPC Detail, 22 Op. O.L.C. at 105. The purpose of these
duties is to allow military personnel to provide support for ongoing civil-
ian law enforcement activities in which CBP personnel take the lead role.
There is no sense in which DoD’s support would pervade CBP’s activi-
ties.
   The federal courts have recognized that DoD’s actions will not be per-
vasive where they merely provide support to civilian law enforcement. In
Yunis, 681 F. Supp. at 895, the district court held that the Navy’s in-

perform no investigative activities and would not be within the chain of custody of
evidence.

                                        22
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
volvement in the apprehension, arrest, and transportation of the defendant
did not “pervade the activities of civilian authorities” because “it was a
civilian operation originating from within the FBI.” Further, “[u]nder the
direction of the FBI,” Navy personnel never participated in the arrest or
interrogation of the defendant, and the Navy merely “gave the necessary
support in the form of equipment, supplies, and services.” Id. at 895; see
also Yunis, 924 F.2d at 1094 (same). More recently, in United States v.
Holloway, 531 F. App’x 582 (6th Cir. 2013) (per curiam), the court held
that the actions of a Naval officer in discovering and notifying civilian
law enforcement of the defendant’s possession of child sexual abuse
material did not “permeate” civilian law enforcement because, “after the
Navy agent turned over the information she had on Holloway to the civil
authorities, the military was not involved in the subsequent search of his
home, the seizure of evidence, or his arrest.” Id. at 583; see also Hayes,
921 F.2d at 103 (actions of military personnel did not pervade civilian law
enforcement because, despite sharing information with the police and
offering other aid, they “did not become involved in any of the activities
typically performed by the police, namely the arrest, the search of the
premises where the transaction occurred, the seizure of the evidence, or
the transportation of that evidence to the station for testing”). 14
   As in these cases, the role of military personnel performing the rail-
support and seal-check duties would be strictly limited and peripheral to
the CBP activities that the duties would support—investigative activities
that would be undertaken by CBP personnel and not military personnel.
Military personnel also would operate under the direct supervision of CBP
personnel. The activities of military personnel would not come close to
pervading CBP’s law enforcement activities.

    14 In United States v. Dreyer, 804 F.3d 1266, 1275 (9th Cir. 2015), the court held that

the military “investigation in this case pervaded the actions of civilian law enforcement”
where the personnel “initiated an operation to search for individuals sharing child pornog-
raphy online,” and themselves testified that they conducted an “active” investigation. Id.
at 1275. Unlike in Dreyer, military personnel performing the rail-support and seal-check
duties would not be leading an investigation, but merely assisting CBP in its activities.

                                           23
                            45 Op. O.L.C. __ (Jan. 19, 2021)

                                           III.

   We turn next to the port-of-entry and checkpoint-observer duties. We
believe that these duties fall within the types of activities expressly au-
thorized under chapter 15, see 10 U.S.C. § 274, and, therefore, DoD is
expressly authorized to perform those duties without the need for further
evaluation under the Posse Comitatus Act.
   We understand that military personnel performing these duties would
monitor the output of CBP electronic systems that automatically collect
and process data, such as license-plate information, regarding individuals
and vehicles passing through a port of entry or U.S. Border Patrol check-
point and display an alert message if the system identifies a concern.
Military personnel would perform this duty in an enclosed location, either
in close proximity to the port of entry or checkpoint or from a remote
location. If military personnel see an alert message from the CBP elec-
tronic display, then they would notify CBP personnel who would take
action in response. Military personnel would have no involvement in any
resulting inspection or investigation. 15
   Section 274 is one of several provisions of chapter 15 that authorize the
military to provide certain assistance to civilian law enforcement. Con-
gress originally enacted section 274 in 1981, when it added a new sub-
chapter to title 10, specifically concerning DoD support for civilian law
enforcement, in order to provide a legislative clarification of congression-
al intent with respect to the Posse Comitatus Act so as to “maximize[] the
degree of cooperation between the military and civilian law enforcement.”
Military Use of Infrared Radars, 15 Op. O.L.C. at 45 (quoting H.R. Rep.
No. 97-71, pt. 2, at 3 (1981)); Department of Defense Authorization Act,
1982, Pub. L. No. 97-86, § 905(a)(1), 95 Stat. 1099, 1115 (1981). Any

   15 Military personnel additionally would be expected to visually observe and maintain
situational awareness of their port-of-entry or checkpoint environments and to notify CBP
personnel of anything suspicious. We understand that, to fulfill this expectation, military
personnel would merely report any suspicious activity observed while doing their job.
This additional aspect of the duty is expressly authorized by 10 U.S.C. § 271(a), which
allows military personnel to provide “any information collected during the normal course
of military training or operations that may be relevant to a violation of any Federal or
State law within the jurisdiction of such officials.” We think that support provided under
chapter 15 would itself be a military operation.

                                           24
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
support for civilian law enforcement that is authorized by section 274 is
expressly authorized for purposes of the Posse Comitatus Act (although
such activities must be done consistent with the regulatory restrictions
required by section 275). See Domestic Terrorism at 3‒5.
   Section 274 authorizes DoD to provide support in the form of operating
equipment. Section 274(b)(1) authorizes DoD, “upon request from the
head of a Federal law enforcement agency, [to] make Department of
Defense personnel available to operate equipment” for the purpose of
enforcing, among other laws, criminal violations of immigration and
customs laws. 10 U.S.C. § 274(b)(1)(A), (b)(4)(A). Section 274(b)(2)
requires that such support may be provided only for certain specifically
listed purposes, but none of those purposes encompasses the full range of
the port-of-entry and checkpoint-observer duties. 16 Section 274(c), how-
ever, contains a catch-all provision specifying that military personnel may
“operate equipment for purposes other than described in subsection
(b)(2)” if “such support does not involve direct participation by such
personnel in a civilian law enforcement operation unless such direct
participation is otherwise authorized by law.”
   We think that the port-of-entry and checkpoint-observer duties are au-
thorized by section 274(c). Military personnel would perform these duties
by operating CBP electronic equipment in an enclosed location and re-
porting upon alert messages that may indicate the possibility of unlawful
conduct. We understand that CBP personnel use the information gathered
in these operations to detect violations of the criminal immigration and
customs laws. These duties thus would involve the use of military person-
nel “to operate equipment” with respect to criminal violations of immigra-
tion and customs laws, as authorized by 10 U.S.C. § 274(b)(1)(A). See
also id. § 274(b)(4)(A) (listing applicable criminal laws).

   16 The closest potentially applicable purpose specified in section 274(b)(2) is the
“[d]etection, monitoring, and communication of the movement of surface traffic outside
of the geographic boundary of the United States and within the United States not to
exceed 25 miles of the boundary if the initial detection occurred outside of the boundary.”
10 U.S.C. § 274(b)(2)(B). We understand, however, that some of the activity here would
not fit within that purpose because it would involve monitoring surface traffic moving
well within the boundaries of the United States, and in some instances at checkpoints that
are more than 25 miles away from the border.

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                       45 Op. O.L.C. __ (Jan. 19, 2021)

   These activities, moreover, would not “involve direct participation by
such personnel in a civilian law enforcement operation.” Id. § 274(c). We
read this language in parallel with the restriction on “direct participation”
required under 10 U.S.C. § 275. See Military Use of Infrared Radars, 15
Op. O.L.C. at 46. As discussed above, that reference codifies the “direct
active participation” test for whether military activity violates the Posse
Comitatus Act. See Domestic Terrorism at 4; Electronic Surveillance at 8;
see also supra Part I (describing the three tests). The text of section
274(c) is materially similar to section 275 insofar as both bar the military
from engaging in “direct participation,” either categorically “in a civilian
law enforcement operation,” 10 U.S.C. § 274(c), or in the slightly more
specific “search, seizure, arrest, or other similar activity,” id. § 275.
   We do not think that the port-of-entry and checkpoint-observer duties
involve direct participation in a civilian law enforcement operation. As
discussed above, the operation of surveillance equipment by military
personnel, such as monitoring an infrared radar surveillance system, or
operating airborne surveillance equipment, does not itself constitute
“direct participation” in civilian law enforcement. See supra Part II.B.2.
In 2002, for example, we concluded that military personnel may assist an
FBI domestic terrorism investigation by piloting an airplane that carried
surveillance equipment, operating the surveillance equipment, and trans-
mitting the imagery to the FBI, with FBI personnel responsible for the
overall conduct of the investigation, including directing the aircraft to
focus on particular targets. See Domestic Terrorism at 2, 4. And in 1994,
we concluded that military personnel do not engage in direct participation
in civilian law enforcement activities in serving “as contemporaneous
monitors of electronic surveillance transmissions.” Electronic Surveil-
lance at 2. We explained that such “remote monitoring through various
forms of electronic assistance” was “distinct from such activities as
‘planting’ the surveillance equipment at the targeted location or carrying
a concealed recording device while acting as an undercover agent.” Id.
at 2, 8. As in these instances, the port-of-entry and checkpoint-observer
duties would not involve “physical contact with civilians or their proper-
ty.” Domestic Terrorism at 4 (quotation marks omitted); see also Elec-
tronic Surveillance at 8; Military Use of Infrared Radars, 15 Op. O.L.C.
at 48.

                                     26
   Military Support for Customs and Border Protection Along the Southern Border
                           Under the Posse Comitatus Act
   The port-of-entry and checkpoint-observer duties would involve the use
of military personnel “to operate equipment” with respect to criminal
violations of immigration and customs laws, 10 U.S.C. § 274(b)(1), and
would not involve “direct participation” in civilian law enforcement, id.
§ 274(c). Therefore, such assistance is expressly authorized for purposes
of the Posse Comitatus Act by section 274. 17

                                             IV.

   We conclude that neither chapter 15 of title 10 of the United States
Code nor section 1059 of the FY 2016 NDAA expressly authorize the
rail-support and seal-check activities for purposes of the Posse Comitatus
Act, but that neither of those activities would involve the use of the mili-

    17 We also think that the port-of-entry and checkpoint-observer duties are consistent

with DoD Instruction 3025.21, which codifies the restriction on “direct participation”
with more particularized restrictions on “direct civilian law enforcement assistance,” id.
encl. 3, ¶ 1.c. Some of those restrictions simply track the terms contained within 10
U.S.C. § 275, such as “search,” and should be construed in the same fashion. Enclosure 3
of this Instruction introduces a new term by restricting DoD personnel from engaging in
“surveillance or pursuit of individuals, vehicles, items, transactions, or physical locations,
or acting as undercover agents, informants, investigators, or interrogators.” DoD Instruc-
tion 3025.21 encl. 3, ¶ 1.c(1)(f ). We view this reference to “surveillance” to encompass
only the kinds of activities that involve “direct civilian law enforcement assistance,” such
as the targeting and tracking of specific individuals. The regulation pairs the term “sur-
veillance” with “pursuit,” “acting as undercover agents, informants, investigators, or
interrogators,” and we thus must read “surveillance” to bear a similar meaning to these
neighboring words. See, e.g., Yates v. United States, 574 U.S. 528, 543 (2015) (stating
that “the principle of noscitur a sociis” counsels that “a word is known by the company it
keeps”). If “surveillance” were construed more broadly, then it would prohibit DoD from
engaging in activities that are plainly authorized under the regulation, such as the
“[d]etection, monitoring, and communication of the movement” of sea, air, and surface
traffic near the border. Id. encl. 3, ¶ 1.d(5)(b)(1)‒(2). Thus, we do not think that either the
port-of-entry or checkpoint-observer duties involve impermissible “surveillance” under
the regulation.
    DoD Instruction 3025.21 also prohibits military personnel from conducting a “search.”
Id. encl. 3, ¶ 1.c(1)(b). As with the regulation’s prohibition of “surveillance,” we read this
portion of the regulations to apply only to a “search” that would constitute “direct civilian
law enforcement assistance,” which, for reasons noted above, the rail-support and seal-
check duties would not involve. While the rail-support and seal-check duties could be said
to involve a “search” in some sense, we do not believe that they would involve a “search”
as that term is used in this regulation. See supra Part II.B.2.

                                             27
                      45 Op. O.L.C. __ (Jan. 19, 2021)

tary “as a posse comitatus or otherwise to execute the laws,” 18 U.S.C.
§ 1385, so as to violate that Act. We further conclude that the port-of-
entry and checkpoint-observer activities are expressly authorized by 10
U.S.C. § 274(c).

                                     STEVEN A. ENGEL
                                   Assistant Attorney General
                                    Office of Legal Counsel

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