Diplomatic Immunities and Privileges: The Continuing Relevance of the Functional Necessity Theory

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Prof. Hayatullah Khan Khattak[1]


(The recent abduction of the Pakistani ambassador to Afghanistan by non-sate actors has sharply brought into focus the vulnerability, and violability, of the diplomatic person. But the inviolability principle on the whole is adhered to by states because reciprocity is a powerful principle although there have been some derogations which states have attempted to justify on the basis of national legislation arising from terrorism. This article examines the various theories as to why states continue to accord diplomatic immunities and privileges in accordance with the Vienna Convention on Diplomatic Relations (1961) regulating diplomatic relations. It is concluded that the functional necessity theory continues to be relevant in justifying state acceptance of immunities and privileges. Author)


Since the beginning of interaction between civilisations, leaders have understood the importance of the inviolability of their emissaries in times of war and peace.[1]This recognitionwas essential to facilitate intercourse[2]with different civilisations in order to advance mutual interests.[3] As far as can be ascertained, the basis for the inviolability of the foreign envoy in antiquity rested on religious grounds.[4]Prior to the emergence of the modern state system in the 17th century, prominent writers of the school of the law of nature sought to explain the juridical basis of the inviolability of the foreign envoy by emphasising its customary nature and this concept was common to all nations.[5] With the establishment of permanent missions in foreign territories there was a corresponding need to determine the juridical basis for inviolability in order to develop the law concerning diplomatic immunities and privileges.[6]Three main theories namely, those pertaining torepresentative character, exterritoriality and functional necessityhave been referred to in this analysis of the various treatises on the law of nations during the sixteenth and seventeenth centuries.[7]Referencesto several of these theories are often found in the same treatisewhich implies that they are inextricably intertwined and ought to be understood in their combined form. Where they were most relevant to the prevalent political conditions, each theory in turn has been dominant over the others in different periods. In explaining the phenomenal exception to the principle of territorial jurisdiction that the law of diplomatic immunities and privileges offers to diplomatic agentseach of the three theories has been very useful. However, the extent to which they offer a sound legal justification for the granting of diplomatic immunities and privileges calls for a closer examination.

This paper outlines the different theories and shows how they have developed in practice. It will enable us to determine the extent to which the theories were important to the development of the law governing diplomatic immunities and privileges and what their fallacies are in providing a juridical basis. It argues that functional necessity has always been the juridical basis for the inviolability of the diplomat, and that his immunity from jurisdiction and his privileges are derived from that principle of inviolability. Therefore functional necessity provides a theoretical justification for the granting of diplomatic immunities and privileges.

Representative Character

The representative character of a foreign envoy predates the establishment of permanent missions and is recognized as a natural attribute because he represents the will or interests of those who sent him. This theory is rooted in history[8] and through it several theories have been identified in the modern development of the law in order to derive a legal explanation for diplomatic immunities and privileges.[9] Essentially, these centre on the direct relationship between the sovereign and his agent, i.e., the ambassador, as well as the sovereign and independent positions that states enjoy under international law which is essential for the preservation of peace and friendly relations among states.[10]

The direct relationship between the sovereign and his ambassador implies that the sovereign regards him as his own personal agent, therefore the ambassador is to be treated with the same respect and dignity as one would expect to give to his prince. The preservation of the honour due to the sovereign played a most significant role, not just on part of the receiving state, but also on the part of the envoy employed.[11] While this is not a legal explanation for diplomatic immunity, the freedom from territorial jurisdiction of the receiving state that a representative of a foreign sovereign must enjoy has later been asserted on the basis of the principle of international law which provides for independence and equality of states.[12] Hence, neither a sovereign nor his representative can be subject to the will or laws of another sovereign. The sovereign’s “right of embassy” seems to have been derived from the same principle of absolute independence.[13] Thus, where a sovereign has a right to send an ambassador to another state, the ambassador enjoys freedom from local jurisdiction not just for reasons of representing another sovereign but also on the basis that his subjection to the laws of another sovereign is incompatible with his duties of representing, rightfully, the interests of his master[14] and effectively undermines his loyalty to him. Due to the sensitivities of monarchs in relation to their sovereignty, observance on the part of the receiving state of the ambassador’s immunities from jurisdiction was essential in order to preserve peace and friendly relations between states.[15] Disregard for the ambassador’s inviolability could lead to war, although this did not mean that the ambassador was free to commit serious crimes as Grotius’ statement on the subject indicates:

“the security of ambassadors is a matter of much greater moment to the public welfare than the punishment of offences. Because reparation for the misconduct of an ambassador may be looked for from the sovereign, by whom he is sent, unless that sovereign chooses to expose himself to hostilities by approving of his crimes.”[16]

When state power was vested in individuals, such as a monarch, the theory provided a justification for the grant of immunities and privileges to an ambassador, since the spread of religious tolerance made any justification for the ambassador’s inviolability on the grounds of religious sanctity obsolete.[17] During the eighteenth century Bynkershoek relied heavily on the writings of Grotius and developed what Grotius used as a way of explanation into a theory of representative character in conjunction with Vattel among others.[18] Their works were based on contemporary state practice[19] and both Vattel and Bynkershoek have emphasised the importance of the direct relationship between the ambassador and the sovereign as well as the  equality and independence of states in order to establish the legal reasons behind the immunities granted to an ambassador as can be seen from the following:

“…an ambassador is not the subject of him to whom he has been sent but remains the subject of him who has sent him. On this account he is not regarded as subject to the jurisdiction of him in whose country he is serving as an ambassador, whether it is a debt or a crime.”[20]

This statement has a different effect from that of Grotius quoted above as it does not just justify the inviolability of the ambassador but grants him immunity from jurisdictionbecausehe is the subject of another sovereign. The foregoing and for the reason that sovereigns considered it a personal insult if one of their representatives was arrested or prosecuted prompted England in 1708 to adopt the Diplomatic Privileges Act. This granted total immunity from criminal and civil prosecution so that ambassadors and their families could exercise their native country’s diplomatic will without fear of repercussions from the host country. TheAct remained in force until the adoption of the Diplomatic Privileges Act 1964, implementing the Vienna Convention 1961.[21]

Vattel describes the “Right of Embassy” as a right that sovereign states possess according to the principle of equality and independence of the law of nations.[22]He implies the following immunities and privileges to be granted to the ambassador from this principle:

“… to the success of his ministry, he must be independent of the sovereign authority and of the jurisdiction of the country, both in civil and criminal matters.”[23]

“To admit a minister, to acknowledge him in such character, is engaging to grant him the most particular protection, and that he shall enjoy all possible safety.”[24]

How then, in the light of the principle of equality and independence of states, can we reconcile the right of embassy and the right of territorial jurisdiction, when the first necessarily restricts the second? In order to find an alternative legal basis for the granting of immunities and privileges, Marshall C. J. reasoned in his judgment of The Schooner Exchange v McFaddon[25] that any limitations on a state’s right to absolute territorial jurisdiction must be imposed by itself, and that a tacit consent between states must exist in order to grant immunities and privileges to sovereigns and their representatives.

Although the “tacit consent” [26]theory is useful in explaining the reciprocal nature of the conduct of diplomatic relations, it has been pointed out that it is a legal justification, convenient to grant immunities and privileges, as opposed to being a juridical basis upon which one can grant immunities as well as impose restrictions upon them. Similarly, the major fallacy of the representative character theory in general is that it lacks adequate mechanisms that may limit immunities and privileges in order to ensure that they cannot be taken advantage of or exaggerated to an extent that would distort the whole idea of diplomatic relations. The basis upon which immunities and privileges for foreign representatives are derived from those of the sovereign seemed to be a logical explanation in times where state power was vested in individuals who could claim to possess the prerogative of sending ambassadors as their personal agents. Nowadays, this concept is outdated as state power in many civilisations is vested in the nation; leaders derive their legitimacy from its citizens and therefore represent the will of their nation.[27] The effect of changing political frameworks has clearly weakened the theory, although it has not invalidated the theory because ambassadors sent by democratic states can equally represent the interests of the nation which is a sovereign entity. As the number of democratic countries grew, the direct relationship between the ambassador and the sovereign diminished and so did the strength of the representative character theory. When representing the interest of the democratic state, it can be implied that diplomatic acts are official acts only as opposed to official and private acts,[28] which could easily be covered by sovereign immunities conferred to ambassadors and his suite. In modern times, therefore, the theory of representative character can only be regarded as an important element of an adequate theory which can form the juridical basis of diplomatic immunity and privileges, rather than being a theory in its own right.


The concept of extra-territoriality was used to explain the exemption from jurisdiction accorded to diplomatic envoys in the state to which they were accredited. In the period where jurisdiction became a territorial concept and sovereigns would consider absolute jurisdiction over their territory as their right, as opposed to personal jurisdiction which was in place when the idea of feudal over-lordship was the custom,[29] the theory provided for an ideal explanation of the exemption from jurisdiction that foreign representatives enjoyed. It could be easily understood that an ambassador was not the subject of the law when on a mission abroad because he was held to actually be in the country of the sovereign who sent him. The concept extended not only over the ambassador and his suite but also to include their homes and the premises of the mission.[30] Originally intended to explain the inviolability of the foreign envoy by Grotius, the concept was developed into a theory to provide a juridical basis for their immunities and privileges.[31] It is clear that once the term was accepted as having legal effect and that embassy premises were in actuality the soil of the sovereign that established it, the legal consequences that arose led to the exaggeration of the immunities and privileges accorded to those involved in diplomatic relations. The idea was so popular and so widely understood by persons that were not part of the diplomatic mission, that businessmen thought that if they concluded a contract on embassy premises, it would be in their favour as the law of the country maintaining the embassy would govern their agreement.[32] Couples living abroad sought to have their wedding performed on embassy grounds belonging to their country of origin for similar reasons.[33] During the seventeenth and eighteenth century criminals or debtors sought refuge in areas surrounding the embassy’s premises; this was a consequence of the most exaggerated application of the extra-territoriality theory known as franchise du quartier which existed in order to protect embassies in areas with political instability such as previously in Rome or Madrid.[34] The application of the extra-territoriality theory can be said to have been varied and inconsistent, it has seen some reduction but it actually survived until the beginning of the twentieth century when jurist concerned with the codification of the law of diplomatic immunities and privileges rejected the theory as a whole.[35]

In the outline above it has been mentioned that the theory of extra-territoriality wasadvanced as a way of explaining theexemption ofthe ambassador from jurisdiction in the country he was accredited to by Grotius:

“ In consequence, by a similar fiction, ambassadors were held to be outside the country to which they were accredited.”[36]

Grotius’ famous words quoted above were misinterpreted by jurists that followed him.The works of Bynkershoek, Vattel and others have particularly been criticized for contributing to the development of this “fiction” into a theory,[37] although various writers have observed that these great jurists placed greater value upon the representative character theory for ascribing a juridical basis to immunities and privileges.[38] It is arguable that Grotius’ statement, as well as existing state practice, may have influenced him to include the notion of extra-territoriality in his work. In fact Ayrault, writing in the sixteenth century, is said to be the first to have asserted the fiction of extra-territoriality which he took from Roman law.[39]

The right of embassies to grant asylum on grounds of extra-territoriality was claimed by many envoys.[40]This may have been the consequence of the application of franchise du quartier and arguably led to the notion of extra-territoriality as a legal circumstance. A clear illustration of the application of the theory having legal consequences can be found in several cases. In Taylor v. Best[41]it was held that, “the foundation of the principle is that the ambassador is supposed to be in the country of his master” and in Magdalena Steam Navigation Co. v Martin,[42]for example, the court accepted that the ambassador is supposed to be residing in his own country “for all intents or purposes.”

Although the theory of extra-territoriality survived until the twentieth century, its application was modified and its exaggerated effect reduced.[43] Extra-territoriality covered only diplomatic personnel or the premises of the embassy itself and was used more as a tool in order to ensure the inviolability of the envoy and his premises.[44] The theory saw diminished application because its validity as a sound juridical basis for immunities and privileges eroded.

Jurists faulted the concept of extra-territoriality because the term could apply to several  situations; it could be used to express the immunities and privileges accorded to diplomatic personnel or it could mean that actions of diplomatic personnel were governed by the law of the sending state.[45] With the exception of the right to grant asylum, which some countries secured by signing multi-lateral treaties,[46] the theory was generally abandoned. In an effort to codify the law governing diplomatic immunities and privileges, the Experts Committee of the League of Nations in 1926 expressly rejected the theory stating that it:

“… does not consider that the conception of ex-territoriality, whether regarded as a fiction or given a literal interpretation, furnishes a satisfactory basis for practical conclusions.”[47]

Furthermore, it fails to provide any means of restricting the diplomatic immunities inherent in the representative character theory. History has shown that it was often used for actions of foreign representatives which were not part of their duty and,farfetched though it may seem today,could also be readily used to establish the jurisdiction of the sending state within the receiving state. Admittedly, the theory provided a mechanism for the protection of diplomatic   premises and personnel during political upheavals. However,it cannot be denied thatit became controversial because of the misinterpretations, or rather convenient interpretations, of the treatises written, among others, by Grotius, Bynkershoek and Vattel. This, by itself demonstrates that extra-territoriality was never meant for use as a theory but merely as a metaphor.

Functional Necessity

In the introduction it was stated that leaders have always been aware that they could not do without messengers or representatives. Essentially, they fulfil the important function of maintaining a line of communication between civilisations, which is indispensible for the furtherance of relations. In times of peace such communication facilitated mutual progress and in times of war, it was needed to end the conflict.[48] The inviolability of the messenger was, therefore, of paramount importance to maintain this line of communication for,without it, the fallout would be negative both for the sending as well as the receiving party. This is a more pragmatic reason than that of the representative character theory, namely that sovereigns of any state would not tolerate an insult against their person or their personal agent, as that could even result in hostilities. Functional necessity may, therefore, be regarded as being the cause of diplomatic immunity. The modern development of the law of diplomatic immunities which began in the sixteenth century was influenced by the school of the law of nature.[49]It argued that religion by itself could not provide a legal explanation for the immunities of an ambassador and, therefore, established the principle that envoys, because of their important functions,had to be protected by natural law.[50]Against this background the development of the law governing diplomatic immunities and privileges gravitated increasingly towards the principle of functional necessity and ultimately led to the restrictive attitude taken by the courts and jurists in the nineteenth century and provided the cornerstone for the twentieth century Convention on the subject. The Vienna Convention on Diplomatic Relations 1961 clearly espouses a functional approach in its Preamble:

“… that the purpose of such privileges and immunities is not to benefit individuals but to ensure the efficient performance of the functions of diplomatic missions as representing states, …”

Early writers such as Ayrault relied on the natural law when establishing that immunity for ambassadors is, in part, derived from functional necessity.[51] Grotius similarly took into account the functional necessity of foreign representatives. He neither considered representative character nor extra-territoriality to be the overriding principles for establishing immunities and privileges but merely used these to illustrate his explanation for the grant of immunities in accordance with the law of nations when he spoke of these “fictions.” When Grotius sought to establish a principle that would justify the inviolability of the ambassador and his property he pointed out that functional necessity is a key element in doing so, as his famously quoted words indicate:

omnio coactio abesse a legato debet, an ambassador ought to be free from all compulsion.”[52]

This principle, which can be found in many of the treatises written on the subject, was applied in the Barbuits Case,[53] for example, where the court used functional necessity in conjunction with representative character when interpreting the Diplomatic Privileges Act 1708. It was held that:“The privilege of a public minister is to have his person sacred and free from arrest, not on his account, but on account of those he represents, and this arises from the necessity of the thing, that nations may have intercourse with one another in the same manner as private persons, by agents, when they cannot meet themselves.”

With the weakening of the representative character and extra-territoriality theories at the end of the nineteenth century, partly due to the democratisation of states, the influence and use of the functional necessity theory grew considerably. Another factor that contributed to this was that states maintained profound relations with one another and began to establish public international organisations such as the League of Nations in the beginning of the twentieth century in order to protect their common interests.[54] As a result, the number of persons involved in maintaining diplomatic relations increased drastically.[55] In these circumstances, functional necessity can address problems such as the correct extent of immunities for administrative personnel whose numbers have undoubtedly risen, and may furnish a better explanation for immunities accorded to servants of diplomatic agents. It was, therefore,only logical that the functional necessity theory influenced the drafters of the Vienna Convention as it enabled restricting immunities and privileges accorded to diplomatic personnel, which were mainly established by the representative character theory.[56]

Although functional necessity is now the recognised basis for immunity as well as a measure for the privileges a diplomat is to be accorded,the theory has been criticizedbecause itis vague and offers little guidance on how it should be applied.[57] It cannot be linked excessively to representative character because that theory equates the diplomat’s immunities and privileges to those accorded to an independent sovereign.[58]It has already been noted that when the representative character theory was dominant the functional necessity element did exist but was eclipsed by the former.As a result the immunities and privileges extended to the diplomatic agent were vast and related to those accorded the sovereign. An alternative interpretation may be a very strict application of the theory which, as a result, would grant immunity only in relation to official acts.[59] While this interpretation may be adequate in some circumstances, particularly with respect to administrative personnel and servants, it is questionable whether it would protect diplomatic agents sufficiently. Moreover, a narrow interpretation would offer little flexibility in regard to changing political circumstances. The bottom line is that the diplomatic agent, whether belonging to a friendly or a hostile country,   must be extended adequate immunities and the highest level of protection.[60]Eras such as the Cold War are good examples where the inviolability of the diplomatic agent would demand the widest interpretation of functional necessity when granting immunities and privileges. Therefore it must be the degree of necessity in order to guarantee the diplomat’s inviolability that has to be primarily considered when determining the extent of immunities and privileges to be accorded to him.


It can be concluded that the theory of representative character in isolation cannot provide a satisfactory juridical basis for the grant of diplomatic immunities and privileges. Its historical influence on the development of the law remains important to this day.However, as it merely explains one aspect of diplomatic relations and can only provide a legal explanation for the grant of immunities and privileges, it must necessarily be complimented by functional necessity which can offer mechanisms for adequate restriction of immunities and privileges. It will be difficult to argue in favour of the theory of extra-territoriality or even find reason for its remaining relevance. As it was so clearly rejected by academics and jurists alike and founded upon an explanation which was not intended to have any legal significance, even a moderate form of continued application of the theory in modern diplomatic relations would not be feasible. It is important to understand the theory in its historical context, the reasons for its application, and why it was so prone to exaggeration, but otherwise it is of no significance and may be termed as a “historical fluke” in the development of the law of diplomatic immunities and privileges. What emerges from this study is that functional necessity is the only theory that can provide a justifiable legal basis for the granting of diplomatic privileges and immunities, even when applied in isolation. I have argued earlier that functional necessity is a useful measure when faced with the interpretation of the degree of immunity and amount of privileges a diplomatic agent must enjoy in order to ensure his inviolability. Since this theory is not just a mechanism that enables the restriction of immunities, but also provides for the allocation of immunities, it can justify the granting of immunities and privileges. A final but important attribute of this theory is that it offers flexibility and can, therefore, stand the test of time.

[1] Prof Hayatullah Khan Khattak is a faculty member of the National Defence University, Islamabad. He also chairs the Directorate of Collaboration and Publication at ISSRA.

[1]E. Young, “The Development of the Law of Diplomatic Relations” (1964) 40 B.Y.I.L. 141

[2]C.E. Wilson, Diplomatic Privileges and Immunities (1967)

[3]Supra, note 1

[4]M. Ogdon, “The Growth of Purpose in the Law of Diplomatic Immunity”, 31 AJIL 449


[6]J.C. Barker, The Abuse of Diplomatic Privileges and Immunities: A Necessary Evil? (1996)

[7]Supra, note 1

[8]G.V. McClanahan, Diplomatic Immunity (1989)

[9]Ogdon, Juridical Bases of Diplomatic Immunity: A Study in the Origin , Growth and Purpose of the Law (1939) Ch. 5





[14]Bynkershoek, Quastionum Juris Publici Libri Duo, Ch. 2 quoted in Ogdon, Juridical Bases of Diplomatic Immunity

[15]Ogdon, Ch. 5d

[16]Grotius (1625), De Jure Belli ac Pacis, Bk. 2, Ch. 18

[17]Supra, note 1

[18]Ogdon, p. 74


[20]Bynkershoek, De Foro Legatorum (1721) p.28 quoted in Barker, The Abuse of Diplomatic Privileges and Immunities: A Necessary Evil?

[21]Barker, Ch. 3

[22]Vattel, Le Droit des Gens (1758) Ch.

[23]Vattel, op cit,

[24]Vattel, op cit,

[25](1812) 7 Cranch 116

[26]Ogdon, op cit, p.119

[27]G.V. McClanahan, Diplomatic Immunity (1989), p. 29


[29]Wilson, p. 5

[30]Ogdon, p.80

[31]Ogdon, p.71

[32]Ogdon, p. 90 illustrates this with the Munir c. Aristarchi-Bey, Tribunal Civil Seine (1909)

[33]Ogdon, p. 83 illustrates this with the Case of Basiliadis, Tribunal Civil Seine (1920)

[34]E. Young, “The Development of the Law of Diplomatic Relations” (1964) 40 B.Y.I.L. 141

[35]Infra, note 48

[36]Grotius, Vol. 2, Bk. 2 Ch. 18 quoted in Barker, The Abuse of Diplomatic Privileges and Immunities: A Necessary Evil?, p. 40

[37]Ogdon, Ch. 4

[38]Ibid., see also Barker, The Abuse of Diplomatic Privileges and Immunities: A Necessary Evil?, p. 41

[39]Ogdon, Ch. 4

[40]McClanahan, p. 32

[41]Hilary term, 17 Victoria (1854), 14 C.B. 487, 517 quoted by Ogdon, p. 79

[42]Court of Queens Bench, 1859; 2 Ellis and Ellis Reports 94, 107, as quoted by Ogdon, p. 80

[43] Wilson, p. 8

[44] Ibid.

[45]Wilson, p. 14

[46] McClanahan, p. 31

[47]op cit, E. Stowell, ” Diplomatic Privileges and Immunities” (1926) 20 AJIL 735

[48]E. Young, “The Development of the Law of Diplomatic Relations” (1964) 40 B.Y.I.L. 141

[49]Supra, note 4


[51]Ogdon, p. 197

[52]Grotius, Vol. 2, Bk. 2 Ch. 18 quoted by Wilson, Diplomatic Privileges and Immunities

[53]Case in Chancery, Cases T. Talbot, 281; 25 Eng.  Reports quoted by Ogdon, Juridical Bases of Diplomatic Immunity, p. 172

[54]L. Preuss, “Diplomatic privileges and Agents Invested With functions of an International Interest” (1931) 25 AJIL 694


[56]Barker, Ch. 3

[57]Wilson, p. 21

[58]Ogdon, p. 176


[60] McClanahan, p. 33