https://crsreports.congress.gov
March 28, 2022
U.S. Nationals and Foreign Military Service
Background
International law grants rights to and imposes duties upon a
neutral state during an armed conflict between belligerent
nations. One of these duties is that neutral states shall not
furnish troops to belligerent states, except this duty does not
include independent actions by a neutral state’s citizens. A
state’s neutrality is usually unaffected if its citizens
willingly serve in a belligerent state’s armed forces.
International law permits such service, but a state’s internal
law may prohibit it. U.S. nationals (including both citizens
and other persons owing allegiance to the United States (8
U.S.C. §1101)) have performed foreign military service at
various times since 1788. This In Focus examines the laws
governing U.S. national foreign military service during
armed conflicts.
Neutrality Act of 1794
The principle that a state may lose its claim to neutral status
if it fails to prevent in its territory a belligerent state’s troop
recruitment or military expeditions is a contribution to
international law originally posited by the United States in
1793 through George Washington and Thomas Jefferson. A
year later, this principle became federal law as part of the
Neutrality Act of 1794. Observers debate whether the
principle of neutrality continues to be viable as customary
international law. The Neutrality Act remains enforceable,
however, and generally prohibits the fitting out of vessels of
war or the launch of an expedition from a U.S. territory to
engage in hostilities abroad.
Among other things, the Neutrality Act prohibits persons
within the jurisdiction of the United States from enlisting in
foreign militaries (18 U.S.C. §959):
Whoever, within the United States, enlists or enters
himself, or hires or retains another to enlist or enter
himself, or to go beyond the jurisdiction of the
United States with intent to be enlisted or entered in
the service of any foreign prince, state, colony,
district, or people as a soldier or as a marine or
seaman on board any vessel of war, letter of
marque, or privateer, shall be fined under this title
or imprisoned not more than three years, or both.
This law apparently applies to anyone in the United States
who joins a foreign military but not those who enlist while
in another country. Accepting a commission while in U.S.
territory from a nation at war against a state with which the
United States is at peace is also prohibited, but this law
applies only to U.S. citizens (18 U.S.C. §958). The United
States has historically prevented enlistment and
appointment activity by other nations within U.S. territory,
but it has rarely enforced these prohibitions against
individuals. On the other hand, U.S. nationals serving in the
military of a nation at war with the United States can be
charged with treason (18 U.S.C. §2381). The enlistment in
foreign service prohibition does not apply to citizens of
countries at war with the United States, except to the extent
they enlist others. The prohibition also does not apply to
transient nationals of belligerent countries. Agreeing with
non-state groups to travel overseas and engage in an
insurgency is not covered by the foreign enlistment law.
Expatriation
Congress has the power to designate certain voluntary acts
by U.S. nationals as expatriating, whereby committing
those acts would result in the loss of U.S. nationality. Since
1941, one such expatriating act has been service in the
armed forces of a foreign state under specific conditions.
The exact conditions necessary for foreign military service
to be expatriating have changed over time, notably with the
enactment of the Immigration and Nationality Act of 1952
(INA) and the 1986 amendments to the INA. One consistent
requirement, however, is that any such foreign military
service must be voluntary—actions taken under duress will
not result in expatriation. The Department of State, in its
Foreign Affairs Manual (FAM), states that conscription into
a foreign military, while not dispositive, “will be considered
as a factor highly relevant to possible duress.”
Historical Expatriation for Foreign Military Service
Under Section 401(c) of the Nationality Act of 1940 (1940
Act), U.S. nationals would lose their nationality by serving
in the armed forces of a foreign state (1) unless expressly
authorized by U.S. law and (2) only if the U.S. national had
or acquired the nationality of the foreign state. Individuals
who were not—or did not become—nationals of the foreign
state were not subject to expatriation.
In 1952, Congress repealed the 1940 Act and replaced it
with the INA. As originally enacted, Section 349 of the
INA provided that U.S. nationals would lose their
nationality by serving in the armed forces of a foreign state
unless such service was “specifically authorized in writing”
by the Secretaries of State and Defense. In contrast to the
1940 Act, the INA required case-by-case authorization,
which, per the FAM, “appears never to have been granted.”
The INA removed the exception for service performed by
individuals who were not also nationals of the foreign state,
instead applying the provision equally to all U.S. nationals.
The INA created a new exception, however, for individuals
who entered foreign military service before the age of 18,
providing for expatriation only if such individuals
voluntarily remained in the foreign military service after
turning 18.
Current Law
Since Congress amended the INA in 1986, a U.S. national
who enters or serves in the armed forces of a foreign state
