How can different and sometimes conflicting norms in IHL and IHRL interact?
As already mentioned, the International Court of Justice has examined the status of human rights in times of international armed conflict0 and occupation0 and found that IHRL continues to apply in these situations. As regards the interaction between international humanitarian law and human rights law in times of international armed conflict (the Congo case) and occupation (the Wall case) the Court has, at a general level, stated that international humanitarian law and human rights law may interact in three possible ways: ‘Some rights may be exclusively matters of international humanitarian law; others may be exclusively matters of human rights law; yet others may be matters of both these branches of international law.’ More specifically, concerning the right to life under international armed conflict, the ICJ found in the 1996 Nuclear Weapons case that the test of what is an arbitrary deprivation of life is to be determined by the applicable lex specialis, namely, the law applicable in (international) armed conflict, which is designed to regulate the conduct of hostilities.
Human rights bodies have also reviewed this issue. In 2001, the UN HRC established in a General Comment that the ICCPR also applies in situations of armed conflict and found that the two spheres of law are complementary rather than mutually exclusive. It went on to state that with respect to ‘certain Covenant rights, more specific rules of international humanitarian law may be especially relevant for the purposes of interpreting the Covenant rights’.   
The European Court of Human Rights considered the issue on the interaction between IHL and IHRL in times of international armed conflict for the first time in the case Hassan v. UK in September 201437 The case concerned the UK detention of an Iraqi national in Iraq in April 2003, in a period when there were still major combat operations—that is, an active IACd8
The UK government contended, among other things, that IHLR, and more specifically Article 5 on detention in the European Convention on Human Rights (ECHR), is ‘displaced by international humanitarian law as lexspecialis, or modified so as to incorporate or allow for the capture and detention of actual or suspected combatants in accordance with the Third and/or Fourth Geneva Conventions, such that there was no breach by the United Kingdom with respect to the capture and detention [of the applicant]’.w
The Court did not accept this view. It stated:
... Consistently with the case-law of the International Court of Justice, the Court considers that, even in situations of international armed conflict, the safeguards under the Convention continue to apply, albeit interpreted against the background of the provisions of international humanitarian law.  
Accordingly, ECHR obligations are not displaced under international armed conflict, but must be interpreted against the ‘background’ of standards in IHL. Thus, IHL functions as lex specialis in international armed conflict in the sense that it elaborates on and suggest modes of application of the broad and general standards in IHRL (general law) in a particular situation. This does not mean that IHRL is displaced.21
In line with this view, the Court held that some of the detention review guarantees found in Articles 5(2) and (4) in the ECHR are still applicable when individuals are detained during international armed conflicts. The detention must be reviewed by a ‘competent body’ which ‘should provide sufficient guarantees of impartiality and fair procedure to protect against arbitrariness. Moreover, the first review should take place shortly after the person is taken into detention, with subsequent reviews at frequent intervals.^
These detention review guarantees are not found in IHL standards on deten- tion/internment, and particularly not for prisoners of war who, under IHL, can be detained for the duration of hostilities without any form of review.23
In situations of non-international armed conflict, it is more difficult to argue that a possible norm conflict between IHL and IHRL should be settled on the basis of the lex specialis principle. Non-international armed conflict is only regulated in treaty law in common Article 3 of the four GCs and in Additional Protocol II (AP II), if it is applicable. Hence, IHL does not provide detailed and precise regulations in non-i nternational armed conflict that can inform standards in IHRL. Furthermore, it is stressed—admittedly in rather ambiguous terms—in the preamble to AP II that human rights are applicable and must be taken into consideration in times of non-international armed conflict.24
The European Court of Human Rights (ECtHR) has also decided a number of cases concerning non-international armed conflict, but the Court has never directly in its reasoning referred to standards in IHL. On the contrary, the Court seems to decide such cases strictly on the basis of the ECHR and does not resort to IHL when interpreting ECHR standards, for example the meaning of the right to life in Article 2.25 In line with this the Court stated in 2014, in the aforementioned case Hassan v. UK, that:
It can only be in cases of international armed conflict, where the taking of prisoners of war and the detention of civilians who pose a threat to security are accepted features of international humanitarian law, that Article 5 could be interpreted as permitting the exercise of such broad powers.26
The UN Office of the High Commissioner for Human Rights has likewise argued that IHRL, and more specifically the right to life, should be considered the lex specialis in times of non-international armed conflict in cases of inconsistency or even conflict with standards in IHL:
Some have interpreted—by analogy with international armed conflicts—that international humanitarian law permits the authorities to shoot to kill [a fighter in non-i nternational armed conflict]. Under international human rights law, a person must be arrested and a graduated use of force must be employed. In this case, taking into account the extent of Government control (if any) over the place where the killing occurs, international human rights law should be considered as the lex specialis?7     
Contrary to this position, the Inter-American Court of Human Rights has applied IHL standards when considering human rights complaints in times of noninternational armed conflict:
[D]uring such situations of internal hostilities, the Commission has received from Colombia and other OAS member States numerous complaints alleging serious violations of the fundamental rights guaranteed in the American Convention and Declaration arising out of the conduct of military operations by State security forces and its other agents. In order to properly judge the specific claims raised in such petitions, the Commission has found it necessary at times either to directly apply rules of international humanitarian law, i.e. the law of armed conflict, or to inform its interpretations of relevant provisions of the American Convention by reference to these rules.2S
The role of IHRL under armed conflict and the relationship with standards in IHL has also been much debated among scholars, with little resulting consensus.29
In summary, there is clearly widespread agreement among judicial review bodies and among states and international organizations regarding the fact that IHRL continues to be applicable and plays an increasingly important role during armed conflict, particularly in non-i nternational armed conflict. On the other hand, it is equally evident that there is little consensus among international complaints bodies, states, international organizations, and scholars on how the different and sometimes conflicting norms in IHL and IHRL can and should interrelate in international and non-international armed conflict. Nevertheless, it can hardly be disputed that IHRL is a relevant legal source in armed conflict and that any new legal instrument—hard law or soft law—dealing with situations of armed conflict and regulating behaviour in armed conflict—no matter what subject matter—would have to reflect international human rights norms, or at the very least to take IHRL into consideration. This is, however, not always the situation in relation to the new soft law instruments concerning IHL, as we shall see in section 3. On the contrary, IHRL norms are often excluded in these new instruments. 
-  UN Human Rights Committee, General Comment No. 29.
-  ECHR, Hassan v. United Kingdom, App. no. 29750/09, 16 Sept. 2014.
-  Major combat operations ended 1 May 2003, see: ECHR, Hassan v. United Kingdom, App.no. 29750/09, 16 Sept. 2014, para. 9.
-  19 ECHR, Hassan v. United Kingdom, App. no. 29750/09, 16 Sept. 2014, para. 88.
-  ECHR, Hassan v. United Kingdom, App. no. 29750/09, 16 Sept. 2014, para. 104.
-  On the function and scope of the lex specialis principle, see e.g.: the International Law CommissionStudy Group on Fragmentation, Koskenniemi, A/CN.4/L.682, 13 Apr. 2006.
-  ECHR, Hassan v. United Kingdom, App. no. 29750/09, 16 Sept. 2014, para. 106.
-  Pursuant to IHL, civilians can be detained for ‘imperative reasons ofsecurity’. For detention reviewstandards in IHL see: Arts 43 and 78(2) in the fourth GC. For more details see: Peter Vedel Kessing,‘Security Detention in Peace Operations’, in Searching for a Principle of Humanity’ in InternationalHumanitarian Law, ed. K. M. Larsen, C. G. Cooper, and G. Nystuen (Cambridge: CambridgeUniversity Press, 2013): 272—304.
-  24 ‘Recalling furthermore that international instruments relating to human rights offer a basic protection to the human person.’
-  Nevertheless, the Court does take into consideration the difficult factual situation in an armedconflict and seems to apply a less strict proportionality test. See e.g.: ECtHR, Ozkan v. Turkey, 6 Apr.2004, paras 305-6.
-  26 ECtHR, Ozkan v. Turkey, 6 Apr. 2004, paras 305-6.
-  UN Human Rights Office of the High Commissioner, ‘International Legal Protection of HumanRights in Armed Conflict’ (New York and Geneva, 2011): 67.
-  8 ‘Third Report on the Human Rights Situation in Colombia’, OEA/Ser.L/V/II.102 Doc. 9 rev. 1,26 Feb. 1999, ch. IV (emphases added). The IACHR has not dealt with situations of internationalarmed conflicts. 29 See e.g.: G. Oberleitner, Human Rights in Armed Conflict (Cambridge: Cambridge UniversityPress, 2015); F. J. Hampson, ‘The Relationship between International Humanitarian Law andInternational Human Rights Law’, in Routledge Handbook of International Human Rights Law, ed. S.Sheeran and N. Rodley (London: Routledge, 2013); O. A. Hathaway et al., ‘Which Law Governs during Armed Conflict? The Relationship between International Humanitarian Law and Human RightsLaw’, Minnesota Law Review vol. 96 (2012): 1883—943; Hans-Joachim Heintze, ‘On the Relationshipbetween Human Rights Law Protection and International Humanitarian Law’, International Review ofthe Red Cross vol. 86 (Dec. 2004); D. Kretzmer, ‘Targeted Killing of Suspected Terrorists: Extra JudicialExecutions or Legitimate Means of Defence?’, European Journal of International Law vol. 16 (2005).