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SPECIAL

REPORT

U. S. INFORMATION SERVICE
PRESS AND PUBLICATIONS BRANCH

TEXT OF A STATEMENT ON LEGAL ASPECTS
OF U. S. MILITARY ACTION IN CAMBODIA
BY JOHN R. STEVENSON, LEGAL ADVISER
OF THE U. S. DEPARTMENT OF STATE
TO THE NYC BAR ASSOCIATION
NEW YORK CITY, MAY 28, 1970

I welcome the opportunity to present the Administration's views on the
questions of international law arising out of the current South Vietnamese and
United States operations in Cambodia. 1
I do not intend to review in any detail the legal justification of earlier
actions by the United States in Vietnam. In 1966 the previous Administration
set forth at some length the legal justifications of our involvement in South
Vietnam and our bombing of North Vietnam. 2 In general, reliance was placed
squarely upon the inherent right of individual and collective self-defense, recognized by Article 51 of the Uo N. Charter. This legal case involved the showing that North Viatnam had raised the level of its subversion and infiltration into
South Vietnam to that of an "armed attack" in late 1964 when it first sent regular
units of its armed forces into South Vietnam. The buildup of American forces
in South Vietnam and the bombing of North Vietnam were justified as appropriate measures of collective self-defense against that armed attack. 3
The legal case presented by the previous Administration was vigorously
attacked and defended by various scholars of the international legal community. 4
Many of the differences rested on disputed questions of fact which could not :)c
proved conclusively. This Administration, however, has no desire to reatrgue
those issues or the legality of those actions which are now history. In January
1969, President Nixon inherited a situation in which one-half million Amurican
troops were engaged in combat in South Vietnam, helping the Republic of Vietnam
May be reproduced with or without attribution to the U. S. Information Seryicf'.

70-52
AMERICAN EMBASSY - TOKYO

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to defend itself against a continuing armed attack by North Vietnam. Our efforts
have been to extricate ourselves from this situation by negotiated settlement if
possible, or, if a settlement providing the South Vietnamese people the right of
self-determination cannot be negotiated, then through the process of Vietnamization. 5 The current actions in Cambodia should be viewed as part of the President's effort to withdraw United States forces from combat in Southeast A aia. 6
I appreciate this opportunity to discuss the questions of international law
arising out of our actions in Cambodia. It is important for the Government of
the United States to explain the legal basis for its actions, not merely to pay
proper respect to the law, but also because the precedent created by the use of
armed forces in Cambodia by the United States can be affected significantly by
our legal rationale. I am sure you recall the choice that was made during the
Cuban missile crisis in 1962 to base our "quarantine" of Cuba not on self -defense
since no "armed attack" had occurred, but on the special powers of the Organization under Chapter 8 of the U. N. Charter, 7 Within a narrower scope the arguments we made can affect the applicability of the Cambodian precedent to other
situations in the future, I believe the United States has a strong interest in the
future. I believe the United States has a strong interest in developing rules of
international law that limit claimed rights to use armed force and encourage the
peaceful resolution of disputes.
One way to have limited the effects of the Cambodian action would have been
to obtain the advance, express request of the Government of Cambodia for our
military actions on Cambodian territory. This might well have been possible 8
However, had we done so, we would have compromised the neutrality of the
Cambodian Government and moved much closer to a situation in which the United
States was committing its armed forces to help Cambodia defend itself against
the North Vietnamese attack. We did not wish to see Cambodia become a cobelligerent along with South Vietnam and the United States. We are convinced
that the interests of the United States, the Republic of Vietnam, and Cambodia,
and indeed the interests of all Asian countries, will best be served by the maintenance of Cambodian neutrality, even though that neutrality may be only partially
respected by North Vietnam.
As the President has made clear, the purpose of our armed forces in
Cambodia is not to help defend the Government of Cambodia, but rather to help
defend South Vietnam and United States troops in South Vietnam from the continuing North Vietnamese armed attack, 9 This limited purpose is consistent
with the Nixon Doctrine, first set forth by the President at Guam on July :35,
1969,10 that the nations of the region have the primary responsibility of providing the manpower for their defense.

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The North Vietnamese have continued to press their attack against South
Vietnam since 1964 and have made increasing use of Cambodian territory in the
furtherance of that attack. They have used Cambodia as a sanctuary for moving
and storing supplies, for training, regroupment and rest of their troops and as
a center of their command and communications network. I assume that these
facts are generally accepted, but it might be useful to give a few examples,
.'\'

In the past five years, 150, 000 enemy troops have been infiltrated i1'to
South Vietnam through Cambodia. In 1969 alone, 60, 000 of their military forces
moved in from Cambodia. The trails inside Cambodia are used not only for the
infil:ration of troops but also for the movement of supplies. A significant quantity
of the military supplies that support these forces came through Cambpdian ports.
Since 1968 the enemy has been moving supplies through southern Cambodia
to its forces in the Mekong Delta. Further, in the spring and summer of 1969,
three to four regiments of regular North Vietnamese troops used Cambodian
territory to infiltrate into the Mekong Delta. Up to that time, there had been
no regular North Vietnamese combat units operating in this area.
As many as 40, 000 North Vietnamese and Viet Cong troops were opel'ating
out of the Cambodian base areas against South Vietnam prior to April 3 0, ,c, s the
war in South Vietnam intensified, Viet Cong and North Vietnamese troops '.''eve
resorted more frequently to these sa1'ctuaries and to attacking from them to
avoid detection by or combat with United States and South Vietnamese forces.
During 1968 and 1969 the Cambodian bases adjacent to the South Vleinan,,'se
provinces of Tay Ninh, Pleiku, and Kontum have served as staging areas for
regimentalsize Communist forces for at least three series of ma~or engageme!:ts - .
the ]968 Tet offensive, the May 1968 offensive and the post-Tet 1969 offensive.
Many of these North Vietnamese actions violate Cambodia!: neutrdJit v.
Flo", ing from the Fifth Hague Convention of 1907 11 are the generally 5..: c~p:Ed
principles that a neutral may not allow belligerents to move troops or supp.~!."CS
across its territory, or to regroup forces on its territory. A neutral is o!:JEgaied
to take positive action to prevent such abuse of its neutrality either by attempiing
to expel the belligerent forces or to intern theIn.
Both the previous Cambodian Government under Prince Sihanouk and tLc
present Government headed by Lon Nol have made efforts to limit, if not prevent,
these violations of Cambodia's rights as a neutral. While the Sihanouk Coven:men! did not, in our judgment, do all that, under international law, it should
have done, it unquestionably made some efforts. As a legal matter it i:; c]"Car

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that a neutral must take active measures commensurate with its power to protect
its territory from abuse by a belligerent. It is likewise clear that a neutral's
"duty of prevention is not absolute, but according to his power. "12 In any event,
however, the control and restraint exercised by the previous Cambodian Government was progressively eroded by constant North Vietnamese pressure. Prior
to the ouster of Prince Sihanouk, regular supply of arms and munitions through
the Port of Sihanoukville had become an established fact.
After the change of government on March 18, in which the United States
was not involved in any respect, Cambodian police and other officials were
driven out of many localities in the border area. When it became apparent to
North Vietnam that the new Cambodian Government was not willing to permit
the same wide scope of unneutral use of its territory by North Vietnamese forces
as the previous Government, the decision was evidently taken to expel all Cambodian Government presence from the border areas and move militarily against
the Cambodian Army, with a view to linking up all the sanctuaries and the Port
of Sihanoukville. This would have produced a unified and protected sanct\lary
from the Gulf of Siam along the entire border of South Vietnam to Laos, with
virtually unrestricted movement and unlimited supply access. The threat
posed by such a situation renewed and increased attacks against United States
and Vietnamese troops in South Vietnam is obvious. We also knew that enemy
forces were instructed to emphasize attacks on U. S. forces and increase U. s.
casual tie s.
That is the rapidly developing situation the President faced at the time of
his April 30 decision to make limited military incursions into the sanctuaries
in Cambodia, which had been militarily occupied by North Vietnam. It was
impossible for the Cambodian Government to take action itself to prevent these
violations of its neutral rights. Its efforts to do so had led to the expulsion of
its forces. In these circumstances, the question arises of what are the rights
of those who suffer from these violations of Cambodian neutrality.
It is the view of some scholars that when the traditional diplomatic remedy
of a claim for compensation would not adequately compensate a belligerent injured
by a neutral's failure to prevent illegal use of its territory by another belligerent,
the injured belligerent has the right of self-help to prevent the hostile use of
the neutral's territory to its prejudice. 13 Professor Castren, the distinguished
Finnish member of the International Law Commission has stated that "If, however,
a neutral state has neither the desire nor the power to interference and the situation is serious, other belligerents may resort to self-help. 13a

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The more conservative view is that a belligerent may take reasonable
actio" against another belligerent violating the neutral's territory only when
required to do so in self-defense. 14
The United States Department of the Army Field Manual relating to the
law of land warfare states the following rule: "Should the neutral state be
unable, or fail for any reason, to prevent violations of its neutrality by the
troops of one belligerent entering or passing through its territory, the other
belligerents may be justified in attacking the enemy forces on this territory. 15
This rule can be traced to, among others, the decision of the Greco-German
mixed arbitral tribunal after the First World War which had to deal with the
German bombardment of Salonika in Greece. During the war the Allied forces
had occupied Salonika despite Greece's neutrality and the Germans responded
with a bombardment. The tribunal stated that Allied occupation constituted
a vio~ation of the neutrality of Greece, and that it was immaterial whether the
Gree:<: Government protested against the occupation or whether it expressly or
tacitly consented to it. The tribunal then concluded that "In either case the
occupation of Salonika was, as regards Germany, an illicit act which authorized
her to take, even on Greek territory, any acts of war necessary for her defense. 1116
When the British Navy entered then neutral Norway's territorial waters
in 19·10 to liberate British prisoners on the Altmark, a German auxiliary vessel,
a tho:~ough analysis of that case by Professor Waldock led him to the conclusion
that in some circumstances a breach of neutrality by one belligerent threatens
the security of the other belligerent in such a way that nothing but the immediate
cessation of the breach will suffice. "Accordingly" -- he continues -- "where
material prejudice to a belligerent's interests will result from its continuance,
the principle of self-preservation would appear fully to justify intervention in
neutr'l.l waters. "17
As far back as the 18th century, Vattel had this to say:
"On the other hand, it is certain that, if my neighbour offers a retreat to
my enemies, when they have been defeated and are too weak to escape me, 'l.nd
allows them time to recover and to watch for an opportunity of making a fresh
attack upon my territory ... (this is) inconsistent with neutrality. " (he) should.
not allow them to lie in wait to make a fresh attack upon me; otherwise he warrants me in pursuing them into his territory. This is what happens when nations
are not in a position to make their territory respected. It soon becomes the seat
of the war; armies march, campaign and fight in it, as in a country open to all
come:~s. "18

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The United States itself has sometimes in the past found it necessary 10
take action on neutral territory in order to protect itself against hostile opel',,tions. Professor Hyde cites many such instances of which I would note Cienu',ol
Jackson's incursion into Spanish West Flcrida in 1818 in order to check 134ttacl,s
by Seminole Indians on United States positions in Georgia; the action taken ag,ur,st
adventurers occupying Amelia Island in 1817, when Spain was unable to exerci se
control over it; and the expedition against Francisco Villa in 1916, after his aHetck
on American territory which Mexico had been unable to prevent. 19
I have summarized these precedents and the views of scholars and gove,"'ments principally to show general recognition of the need to provide a lawfuj and
effective remedy to a belligerent harmed by its enemy's violations of a neutral's
rights. I would not suggest that those incidents and statements by themselves
provide an adequate basis for analysis of the present state of the law. We an
recognize that, whatever the merits of these views prior to 1945, the adoption
of the United Nations Charter changed the situation by imposing new and important limitations on the use of armed force. 20 However, they are surely authority
for the proposition that, assuming the Charter's standards are met, a beUigerent
may take action on a neutral's territory to prevent violation by another belligerent
of the neutral's neutrality which the neutral cannot or will not prevent, providing
such action is required in self-defense.
•
In general, under the Charter the use of armed force is prohibited exc<,pt
as authorized by the United Nations or by a regional organization within the scope
of its competence under Chapter 8 of the Charter, or, where the Security Council
has not acted, in individual or collective self-defense against an armed attack.
It is this latter basis on which we rely for our actions against North Vietn:lm",qe
armed forces and bases in Cambodia.
Sinoe 1965 we and the Republic of Vietnam have been engaged in colleer)\?
measures of self~defense against an armed attack from North Vietnam. Incy "2'~.,
ingly since that time the territory of Cambodia has been used by North V letns,n
as a base of military operations to carry out that attack, and it long ago teaci'E'rl
a level that would have justified us in taking appropriate measures of seH'dc,fE:nS8
on the territory of Cambodia. However" except for scattered instances of rc
turning fire across the border, we refrained until April from taking such <i "tic,n
in Cambodia. The right was available to us, but we refrained from exer,tisir:r
it in the hope that Cambodia would be able to impose greater restraints or: er,,"TlY
use of its territory. However, in late April a new and more dangerolls situ8:islC
developed. It became apparent that North Vietnam was proceeding rapid];.' tt'
remove all remaining restraints on its use of Cambodian territory to conti.r:w' 'b,
armed attacks on South Vietnam and our armed forces there.

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Prior to undertaking military action the United States explored to the
fullest other means of peaceful settlement. We awaited the outcome of the
Cambodian Government's efforts to negotiate with the North Vietnamese and
the Viet Cong agreed limitations on the use by the latter of Cambodian territory
without success. We have continually tried in the Paris talks to bring about
serious negotiation of the issues involved in the war. Soundings in the Security
Coundl indicated very little interest in taking up the North Vietnamese violations
of Cambodian territorial integrity and neutrality. We welcomed the French proposal looking to the possibility of an international conference although not publicly
for fear of discouraging Hanoi's participation. The Soviet Union, after initially
indicating interest, backed away. We were particularly pleased with the calling
of the Djakarta Conference of interested Asian states to deal with the Cambodian
problem on a regional basis. The best long-run approach to East Asian security
problems lies through cooperative actions such as this. In the short run, however,
they 2annot be expected to provide an adequate defense to the North Vietnamese
military threat.
The United States has imposed severe limits on the activities of U. S. forces.
They will remain in Cambodia only a limited time - - not beyond July 1 - - in a
limited area - - not beyond 21 miles from the border - - and with a limited
purpose - - to capture or destroy North Vietnamese supplies, to destroy base
installations, and to disrupt communications. To the maximum extent possible,
we have directed our forces at enemy base areas and have tried to avoid civilian
population centers. We have limited our area of operations to that part of Cambodia from which Cambodian authority had been eliminated and which was occupied
by the North Vietnamese.
The Cambodian Government and the Cambodian people are not the targets
of oue operations. During the period from 1967 to 1970 the Cambodian Government
became increasingly outspoken in its opposition to the North Vietnamese occupation. In fact, Sihanouk's purpose in going to the Soviet Union and China when he
was deposed was to solicit their help in persuading the North Vietnamese to get
out 0:' Cambodia. The Lon Nol Government has expressed its understandil'g of
our actions. 21
.,
Our actions in Cambodia are appropriate measures of legitimate collective
self -defense, and we have so reported to the United Nations, as required bv
Article 51 of the United Nations Charter. 2 2 '
(Footnotes Follow)

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1 - - The views of the Administration on the military and political issues
have been expressed clearly by the President and other officials. See, in
particular, President Nixon's address of April 30, 1970, reprinted in State
Department Bulletin of May 18, and his press conference of May 8, reprinted
in the New York Times on May 9. See also, Deputy Secretary of Defense
Packard's address of May 15, 1970 in Fort Worth, Texas.
2 -- Meeker, liThe Legality of United States Participation in the Defense
of Vietnam", March 4, 1966, submitted to the Senate Committee on Foreign
Relations on March 8, and published in the State Department Bulletin of March
28, 1966.
3 -- They were also justified on that basis in U. S. reports to the United
Nations, pursuant to Article 51. See the texts of the letters from Ambassador
Stevenson to the Security Council, dated February 7 and February 27, 1965,
reprinted in the Department of State Bulletin, Feb. 22, 1965, P. 240, and
March 22, 1965, P. 419.
4 - - See the collection, in two volumes, "The Vietnam War and International Law," Edited by Richard A. Falk, and published in 1968 and 1969
by the American Society of International Law.
5 - - The President reviewed our efforts at negotiation and the progress
of Vietnamization in his statement of April 20,. 1970, published in State Department Bulletin, May 11, 1970 and stated' " ... our overriding objective is at
political solution that reflects the will of the South Vietnamese people and
allows them to determine their future without outside interference. II
6 -- In his address of April 30, announcing the use of force in Cambodia,
President Nixon said: "We take this action not for the purpose of expanding the
war into Cambodia but for the purpose of ending the war in Vietnam, and winning
the just peace we all desire. We have made and will continue to make every
possible effort to end this war through negotiation at the conference table rather
than through more fighting in the battlefield. "
7 -- See Chayes, "Law and the Quarantine of Cuba", Vol. 41 Fon-,ign
Affairs (1963) P. 550.
8 -- On May 1 a Cambodian spokesman said that "The Cambodian Government as a neutral government cannot approve foreign intervention." However,
on May 5, Lon Nol issued the following statement' "In his message to the American
people of April 30, 1970, President Nixon made known the important measures

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which he had taken to counter the military aggression of North Vietnam in Laos,
Cambodia and South Vietnam. One of these measures concerns the aid of the
U. S. in the defense of the neutrality of Cambodia violated by the North Vietnamese.
"The Government of Salvation notes with satisfaction the President of the
United States took into consideration in his decision, the legitimate expressions
of the Cambodian people who only desire to live in peace within their territory,
independent, and in strict neutrality. For this reason, the Government of
Cambodia (GOC) wishes to announce that it appreciates the views of President
Nixon in his message of April 30 and expresses to him its gratitude.
"It is time now that the other friendly nations understand the extremely

serious situation in which Cambodia finds itself and come to the assistance of
the Cambodian people who are victims of armed aggression. The Government
of Salvation renews on this occasion its appeal for assistance made April 14,
noting that it will accept from friendly countries all unconditional and diplomatic,
military and economic assistance. "
Later statements have indicated even more clearly the Cambodian Government's approval of our actions.
9 -- This is to be distinguished from the furnishing of weapons and ammunition 10 Cambodia pursuant to the Foreign Assistance Act, 75 Stat. 424, 22 Vuo S. C,
S216>2410, which is done to improve the ability of Cambodia to defend itself.
10 - - The President's statements were not for direct quotation, but the
]\jew York Times of July 26, 1969 contains a fair summary of his remarks.
The President later clarified the doctrine in his address to the nation on Vietnam
()f Ncvember 3, 1969 and in his report to the Congress dated February 18, 1870
on U,S. foreign policy for the 1970's.
11 - - 1 Bevans, "Treaties and Other International Agreements of the
United States of America" (1968) P. 654.
12 -- As the Harvard Research in International Law pointed out in its
1939 draft convention on rights and duties of neutral states in naval and aerial
war, "A neutral state is not an insurer of the fulfillment of its neutral dLlties.
It is :>bligated merely to 'Llse the means at its disposal' to secure the fulfillment
of itO' dLlties." 33 American Journal of International Law (1939), Suppl., P. 247.

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13 -- According to Greenspan, "The Modern Law of Land Warfare"
(1959) P. 538: "Should a violation of neutral territory occur through the
complaisance of the neutral state, or because of its inability, through weakness
or otherwise, to resist such violation, then a belligerent which is prejudlced by
the violation is entitled to take measures to redress the situation, including, if
necessary, attack on enemy forces in the neutral territory. "
13a - - Castren, "The Present Law of War and Neutrality" (Helsinki, 1954)
P. 442. See also II Guggenheim, '':rraite de Droit International Public" (Geneva,
1~IC4) P. 346.
14 -- II Oppenheim, "International La.w"(7th Ed. 1952) P. 698. This is
true whether or not the neutral has met its obligations to use the means as
its disposal to oppose belligerent use of its territory. Stone, "Legal Controls
of International Conflict" (1954) says (P. 401): "One clear principle is that,
the right of self-preservation apart, an aggrieved state is clearly not entitled
to violate the neutral's territorial integrity, simply because his enemy has
done so. Diplomatic representations and claim are the proper course. II A
Columbia Law Review note concludes: . "Military action within neutral territory
may be justified as a measure of self-defense or as an appropriate response to
the failure of a neutral state to prevent the use of its territory by belligerent
forces. . .. It is suggested ... that international law should permit and encourage
primary reliance on self-defense as a justification." Note, "International Law
and Military Operations against Insurgents on Neutral Territory", 68 Col. L.
Rev. P. 1127 (1948). See also Corfu Channel Case, ICJ reports 1949, Pp. 34-35
and 77.
15 -- FM 27-100 (July 1956) Para. 520, P. 185. Similar proVlslOns
were contained in the U. S. Rules of Land Warfare of 1940 (Para. 366) and
in the British Manual of Military Law (Para. 655). See Greenspan, "The
Modern Law of Land Warfare" (1959) P. 538, N. 23.
16 -- Coenca Brothers V. The German State, 1927, translated in Briggs,
"The Law of Nations: Cases, Documents and Notes" (1938) Pp. 756-58.
17 -- Waldock, "The Release of the Altmark's Prisoners," 24 British
Year Book of International Law (1947) P. 216, at 235-36. See also Tucker,
"The Law of War and Neutrality at Sea" (Naval War College, International Law
Studies, Vol. XLX. 1955, P. 262).

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18 -- 3 E. de Vattel, Le Droit des Gens (renwick Transl. 1916) S133,
at 277 (emphasis added).
19 -- I Hyde, "International Law" (2d Ed., 1945), Pp. 240-44.
20 -- In particular, Article 2, Para. 4 of the Charter.
21 -- See note (8) above.
22 -- ~/9781 (Magtn 1970).