Rule 77. Expanding Bullets
Rule 77. The use of bullets which expand or flatten easily in the human body is prohibited.
Summary
State practice establishes this rule as a norm of customary international law applicable in both international and non-international armed conflicts.
International armed conflicts
The prohibition in respect of international armed conflicts was introduced in 1899 by the Hague Declaration concerning Expanding Bullets in reaction to the development of the so-called “dum-dum” bullet for use in military rifles.[1]  The Declaration was ratified or acceded to by 28 States in the early years of the 20th century and 6 States succeeded to the Declaration in the second half of the 20th century.[2]  The use of expanding bullets is listed as a war crime in the Statute of the International Criminal Court.[3]  The prohibition has also been included in other instruments.[4] 
The prohibition of expanding bullets is set forth in numerous military manuals.[5]  The use of expanding bullets in armed conflict is an offence under the legislation of many States.[6]  The prohibition is also supported by official statements and other practice.[7]  This practice includes that of many States which are not party to the Hague Declaration.[8] 
Practice is in conformity with the prohibition and no State has asserted that it would be lawful to use such ammunition. The only exception to a complete prohibition of the use of expanding bullets is possibly the practice of the United States, although it is ambiguous. While several of its military manuals prohibit the use of expanding bullets,[9]  three legal reviews of ammunition and weapons by the US Department of the Army state that the United States will adhere to the Hague Declaration to the extent that the rule is consistent with Article 23(e) of the 1907 Hague Regulations, i.e. the prohibition of weapons causing unnecessary suffering.[10]  Hence, the use of expanding ammunition is lawful according to the United States if there is “a clear showing of military necessity for its use”.[11]  However, during the negotiation of the Statute of the International Criminal Court in 1998, the United States did not contest the criminality of the use of expanding ammunition.
Non-international armed conflicts
The prohibition of expanding bullets in any armed conflict is set forth in several military manuals.[12]  The use of expanding bullets is an offence under the legislation of several States.[13]  Colombia’s Constitutional Court has held that the prohibition of “dum-dum” bullets in non-international armed conflicts is part of customary international law.[14] 
Practice is in conformity with the rule’s applicability in both international and non-international armed conflicts, as the same ammunition is used in non-international conflicts as in international conflicts, and bullets which expand or flatten easily in the human body are not employed in either case. That this general abstention is not purely coincidental can be deduced also from the fact that weapons which cause unnecessary suffering are prohibited in both international and non-international armed conflicts (see Rule 70) and that there is general agreement that such bullets would cause unnecessary suffering.[15] 
No official contrary practice was found with respect to either international or non-international armed conflicts. With the possible exception of the United States, no State has claimed that it has the right to use expanding bullets. However, several States have decided that for domestic law-enforcement purposes, outside armed conflict, in particular where it is necessary to confront an armed person in an urban environment or crowd of people, expanding bullets may be used by police to ensure that the bullets used do not pass through the body of a suspect into another person and to increase the chance that once hit, the suspect is instantly prevented from firing back. It should be noted that expanding bullets commonly used by police in situations other than armed conflict are fired from a pistol and therefore deposit much less energy than a normal rifle bullet or a rifle bullet which expands or flattens easily. Police forces therefore do not normally use the type of expanding bullet that is prohibited for military rifles.
The introduction of expanding bullets for police use indicates that States consider such bullets necessary for certain law-enforcement purposes. However, the use of expanding bullets has not been introduced for hostilities in armed conflicts.
Interpretation
As far as the design of the bullets is concerned, a number of military manuals refer to the wording of the Hague Declaration or specify that “dum-dum” bullets (i.e., “soft-nosed” or “hollow-point” bullets) are prohibited.[16]  However, most manuals specifically refer to the fact that the bullet expands or flattens easily, rather than to whether it has a hollow point, soft nose or incisions, as indicated by way of example in the Hague Declaration.[17]  Germany’s Military Manual adds examples of other types of projectiles that create large wounds similar to those caused by “dum-dum” bullets: projectiles of a nature to burst or deform while penetrating the human body, to tumble early in the human body or to cause shock waves leading to extensive tissue damage or even lethal shock.[18]  A memorandum of law on sniper use of open-tip ammunition prepared by the US Department of the Army in 1990 found that a certain type of hollow-point bullet was not unlawful because it did not expand or flatten easily, and the particular circumstances of intended use, namely by army snipers, was justified because of the accuracy at long range that the design allowed.[19] 

[1] Hague Declaration concerning Expanding Bullets (cited in Vol. II, Ch. 25, § 1).
[2] The following states ratified or acceded to the Declaration: Austria-Hungary (4 September 1900), Belgium (4 September 1900), Bulgaria (4 September 1900), China (21 November 1904), Denmark (4 September 1900), Ethiopia (9 August 1935), France (4 September 1900), Germany (4 September 1900), Great Britain and Ireland (13 August 1907), Greece (4 April 1901), Italy (4 September 1900), Japan (6 October 1900), Luxembourg (12 July 1901), Mexico (17 April 1901), Montenegro (16 October 1900), Netherlands (4 September 1900), Nicaragua (11 October 1907), Norway (4 September 1900), Persia (4 September 1900), Portugal (29 August 1907), Romania (4 September 1900), Russia (4 September 1900), Serbia (11 May 1901), Siam (4 September 1900), Spain (4 September 1900), Sweden (4 September 1900), Switzerland (29 December 1900) and Turkey (12 June 1907). The following States succeeded to the Declaration: Byelorussian Socialist Soviet Republic (4 June 1962), Fiji (2 April 1973), German Democratic Republic (9 February 1959), South Africa (10 March 1978), USSR (7 March 1955) and Yugoslavia (8 April 1969).
[3] ICC Statute, Article 8(2)(b)(xix) (cited in Vol. II, Ch. 25, § 2).
[4] See, e.g., Oxford Manual of Naval War, Article 16(2) (ibid., § 3); Report of the Commission on Responsibility (ibid., § 4); UN Secretary-General’s Bulletin, Section 6.2 (ibid., § 5); UNTAET Regulation No. 2000/15, Section 6(1)(b)(xix) (ibid., § 6).
[5] See, e.g., the military manuals of Australia (ibid., §§ 7–8), Belgium (ibid., § 9), Cameroon (ibid., § 10), Canada (ibid., §§ 11–12), Dominican Republic (ibid., § 13), Ecuador (ibid., § 14), France (ibid., §§ 15–17), Germany (ibid., §§ 18–20), Israel (ibid., § 21), Italy (ibid., § 22), Kenya (ibid., § 23), Netherlands (ibid., §§ 24–25), New Zealand (ibid., § 26), Nigeria (ibid., § 27), Russian Federation (ibid., § 28), South Africa (ibid., § 29), Spain (ibid., § 30), United Kingdom (ibid., § 31) and United States (ibid., §§ 33–35).
[6] See, e.g., the legislation of Andorra (ibid., § 36), Australia (ibid., §§ 37–38), Canada (ibid., § 40), Congo (ibid., § 41), Ecuador (ibid., § 42), Estonia (ibid., § 43), Georgia (ibid., § 44), Germany (ibid., § 45), Italy (ibid., § 46), Mali (ibid., § 47), Netherlands (ibid., § 48), New Zealand (ibid., § 50), United Kingdom (ibid., § 52) and Yugoslavia (ibid., § 53); see also the draft legislation of Burundi (ibid., § 39) and Trinidad and Tobago (ibid., § 51).
[7] See, e.g., the statements of Algeria (ibid., § 55), Canada (ibid., § 56), Colombia (ibid., § 57), Egypt (ibid., § 58), Finland (ibid., § 60), Iraq (ibid., § 64), Italy (ibid., § 65), Philippines (ibid., § 67), Sweden (ibid., §§ 68–69), Switzerland (ibid., § 70), United States (ibid., §§ 71 and 73–77) and Yugoslavia (ibid., §§ 78–79), the practice of Indonesia (ibid., § 63) and the reported practice of India (ibid., § 62) and Jordan (ibid., § 66).
[8] See, e.g., the military manuals of Australia (ibid., §§ 7–8), Cameroon (ibid., § 10), Canada (ibid., §§ 11–12), Dominican Republic (ibid., § 13), Ecuador (ibid., § 14), Israel (ibid., § 21), Kenya (ibid., § 23), New Zealand (ibid., § 26), Nigeria (ibid., § 27) and United States (ibid., §§ 33–35), the legislation of Andorra (ibid., § 36), Australia (ibid., §§ 37–38), Canada (ibid., § 40), Congo (ibid., § 41), Ecuador (ibid., § 42), Estonia (ibid., § 43), Georgia (ibid., § 44), Mali (ibid., § 47) and New Zealand (ibid., § 50), the draft legislation of Burundi (ibid., § 39) and Trinidad and Tobago (ibid., § 51), the statements of Algeria (ibid., § 55), Canada (ibid., § 56), Colombia (ibid., § 57), Egypt (ibid., § 58), Finland (ibid., § 60), Iraq (ibid., § 64), Philippines (ibid., § 67) and United States (ibid., §§ 71 and 73–77), the practice of Indonesia (ibid., § 63) and the reported practice of India (ibid., § 62) and Jordan (ibid., § 66).
[9] United States, Field Manual (ibid., § 33), Air Force Pamphlet (ibid., § 34) and Instructor's Guide (ibid., § 35).
[10] United States, Department of the Army, Memorandum of Law on Sniper Use of Open-Tip Ammunition (ibid., §§ 74–75), Legal Review of USSOCOM Special Operations Offensive Handgun (ibid., § 76) and Legal Review of the Fabrique Nationale 5.7x28mm Weapon System (ibid., § 77).
[11] United States, Department of the Army, Legal Review of USSOCOM Special Operations Offensive Handgun (ibid., § 76).
[12] See, e.g., the military manuals of Australia (ibid., § 7), Canada (ibid., § 12), Ecuador (ibid., § 14), France (ibid., §§ 16–17) (“totally prohibited”), Germany (ibid., §§ 18–20), Italy (ibid., § 22), Kenya (ibid., § 23), South Africa (ibid., § 29) and Spain (ibid., § 30) (“absolute prohibition”).
[13] See, e.g., the legislation of Andorra (ibid., § 36), Ecuador (ibid., § 42), Estonia (ibid., § 43), Germany (ibid., § 45) and Yugoslavia (ibid., § 53); see also the legislation of Italy (ibid., § 46), the application of which is not excluded in time of non-international armed conflict.
[14] Colombia, Constitutional Court, Constitutional Case No. C-225/95 (ibid., § 54).
[15] See, e.g., Hague Declaration concerning Expanding Bullets (cited in Vol. II, Ch. 20, § 3); the military manual of Australia (ibid., § 34) (“hollow point weapons”), Ecuador (ibid., § 52), France (ibid., §§ 55–56), Germany (ibid., §§ 57–59), Netherlands (ibid., §§ 71–72), Russian Federation (ibid., § 78), South Africa (ibid., 80), United States (ibid., § 91) and Yugoslavia (ibid., § 94).
[16] See, e.g., the military manuals of Australia (cited in Vol. II, Ch. 25, §§ 7–8), Dominican Republic (ibid., § 13), Germany (ibid., § 18), Israel (ibid., § 21), Netherlands (ibid., § 25), New Zealand (ibid., § 26), South Africa (ibid., § 29), United Kingdom ( ibid., §§ 31–32) and United States (ibid., §§ 33 and 35).
[17] See, e.g., the military manuals of Belgium (ibid., § 9), Cameroon (ibid., § 10), Canada (ibid., §§ 11–12), Ecuador (ibid., § 14), France (ibid., §§ 15–17), Germany (ibid., §§ 19–20), Italy (ibid., § 22), Kenya (ibid., § 23), Netherlands (ibid., § 24), Nigeria (ibid., § 27), Russian Federation (ibid., § 28), Spain (ibid., § 30) and United States (ibid., § 34).
[18] Germany, Military Manual (ibid., § 19).
[19] United States, Department of the Army, Memorandum of Law on Sniper Use of Open-Tip Ammunition (ibid., § 75).