A/HRC/42/CRP.1 do everything feasible to verify that something thought to be a military objective is in fact one.53 77. In addition, unless circumstances do not permit, civilians must be given advance warning of an attack.54 This rule requires the giving of an effective warning. This would imply that the warning is capable of being acted upon. One can envisage the giving of a warning which, in the circumstances, is not capable of being acted upon. It would nevertheless be a warning and should normally be given, subject to the need to avoid terrorizing the civilian population. The formulation of this rule is important. It is not that a warning should be given if feasible. The presumption is that a warning must be given. The purpose of such a rule is to enable civilians to avoid harm either by leaving the area or by taking shelter.55 The attacking party is also required to consider the potential impact of the attack on the natural environment and cannot launch an attack where the foreseeable impact would be disproportionate. This raises an issue which is relevant in every application of the proportionality principle. When considering the foreseeable impact is the attacking party entitled to assume that everything will work as planned; that weapons will function as they are supposed to do and that protective measures round an installation will function as they are supposed to do? If not, what is the test? It is not reasonable to suggest that the attacker must envisage the worst case scenario in which everything goes wrong. Weapon Use 78. It has already been shown that the choice of weapon to be used in an attack will affect the determination of proportionality. There are, in addition, general rules about weapon use. Furthermore, certain weapons are the subject of specific bans or specific regulation of their use. 79. No weapon can be used which is of a nature to cause “superfluous injury or unnecessary suffering” to combatants.56 The other general rules with regard to weapon use ultimately derive from the obligation to protect the civilian population. So, for example, the use of inherently indiscriminate weapons is prohibited on account of the risk they pose to civilians.57 Similarly, the use of a potentially discriminate weapon in an indiscriminate way is also prohibited, as is the use of a weapon, however precisely targeted, which may be anticipated to give rise to excessive casualties. A party to a conflict is not required to use the most precise, “high-tech” weapon in its arsenal to prosecute a particular attack on condition that the weapon used is lawful and the foreseeable consequences of its use are lawful. 80. The lawfulness of weapons or weapons systems in relation to their nature or use has been called into question in the conflict in Yemen in a number of cases, particularly in the shelling, the use of indirect fire weapons in residential areas, and the use by the Houthis of landmines, both anti-vehicle and anti-personnel, without any attempt to take steps to protect the civilian population from their effects. 2. International Human Rights Law 81. As noted in last year’s report58, the Government of Yemen remains responsible for the fulfilment of its human rights obligations in the entirety of its territory, including the parts over which it has lost control. Yemen has the primary obligation to protect the Yemeni population from harmful interference by non-State armed groups, an obligation of due diligence.59 The Human Rights Committee asserted that a State Party also has the 53 ICRC Study on customary IHL, rule 16. ICRC Study on customary IHL, rule 20. 55 Ibid, Volume 2, Part I, Chapter 5F. 56 See generally ICRC Study on customary IHL, rule 70. 57 ICRC Study on customary IHL, rule 71. 58 A/HRC/39/43, para. 13. 59 See e.g., Geneva Academy of International Humanitarian Law and Human Rights, “Human Rights Obligations of Armed Non-State Actors: An Exploration of the Practice of the UN Human Rights Council,” Academy In-Brief No. 7, December 2016 (https://www.geneva-academy.ch/joomlatools54 20