Rule 35. Hospital and Safety Zones and Neutralized Zones
Rule 35. Directing an attack against a zone established to shelter the wounded, the sick and civilians from the effects of hostilities 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 and non-international armed conflicts
The First and Fourth Geneva Conventions provide for the possibility of setting up hospital and safety zones, and a draft agreement for the establishment of such zones is attached thereto.[1]  In addition, the Fourth Geneva Convention provides for the possibility of setting up neutralized zones.[2]  Both types of zone are intended to shelter the wounded, the sick and civilians from the effects of conflict, but the hospital and safety zones are meant to be far removed from military operations, whereas neutralized zones are intended for areas in which military operations are taking place.
The relevant provisions of the Geneva Conventions are incorporated in many military manuals, which emphasize that these zones must be respected.[3]  Under the legislation of several States, it is an offence to attack such zones.[4] 
In a resolution adopted in 1970 on basic principles for the protection of civilian populations in armed conflicts, the UN General Assembly stated that “places or areas designated for the sole protection of civilians, such as hospital zones or similar refuges, should not be the object of military operations”.[5] 
Zones providing shelter to the wounded, the sick and civilians have been agreed upon in both international and non-international armed conflicts, for example, during Bangladesh’s war of independence, the war in the South Atlantic and the conflicts in Cambodia, Chad, Cyprus, Nicaragua, Lebanon, Sri Lanka and the former Yugoslavia.[6]  Most of these zones were established on the basis of a written agreement. These agreements were premised on the principle that zones established to shelter the wounded, the sick and civilians must not be attacked. The neutralized zone established at sea during the war in the South Atlantic (the so-called “Red Cross Box”) was done without any special agreement in writing. A zone which contains only wounded and sick (see Rule 47), medical and religious personnel (see Rules 25 and 27), humanitarian relief personnel (see Rule 31) and civilians (see Rule 1) may not be attacked by application of the specific rules protecting these categories of persons, applicable in both international and non-international armed conflicts.

[1] First Geneva Convention, Article 23 (cited in Vol. II, Ch. 11, § 1); Fourth Geneva Convention, Article 14, first paragraph (ibid., § 2).
[2] Fourth Geneva Convention, Article 15 (ibid., § 3).
[3] See, e.g., the military manuals of Argentina (ibid., §§ 6–7), Australia (ibid., § 8), Cameroon (ibid., § 9), Canada (ibid., § 10), Ecuador (ibid., § 11), France (ibid., §§ 12–13), Germany (ibid., § 14), Hungary (ibid., § 15), Italy (ibid., §§ 16–17), Kenya (ibid., § 18), Madagascar (ibid., § 19), Netherlands (ibid., § 20), New Zealand (ibid., § 21), Nigeria (ibid., § 22), Senegal (ibid., § 23), Spain (ibid., § 24), Sweden (ibid., § 25), Switzerland (ibid., §§ 26–27), United Kingdom (ibid., §§ 28–29), United States (ibid., §§ 30–33) and Yugoslavia (ibid., § 34).
[4] See, e.g., the legislation of Colombia (ibid., § 36), Italy (ibid., § 37), Poland (ibid., § 40) and Spain (ibid., § 41); see also the draft legislation of Argentina (ibid., § 35), El Salvador (ibid., § 38) and Nicaragua (ibid., § 39).
[5] UN General Assembly, Res. 2675 (XXV) (adopted by 109 votes in favour, none against and 8 abstentions) (ibid., § 47).
[6] See, e.g., Memorandum of Understanding on the Application of IHL between Croatia and the Socialist Federal Republic of Yugoslavia (ibid., § 4); Agreement between Croatia and the Socialist Federal Republic of Yugoslavia on a Protected Zone around the Hospital of Osijek, Articles 1, 2(1) and 4(1) (ibid., § 5); the practice concerning the war in the South Atlantic (ibid., § 45), Bangladesh (ibid., § 53), Cyprus (ibid., § 55), Cambodia (ibid., § 56) and Sri Lanka (ibid., § 57); see also François Bugnion, The International Committee of the Red Cross and the Protection of War Victims, ICRC, Geneva, 2003, pp. 756–759 (providing examples from the conflicts in Bangladesh, Cyprus, Cambodia, Nicaragua, Chad and Lebanon among others).