In 2004, Bas van Hoek was about to deliver a lesson on the use of force instructions to service personnel when the case of Erik O. hit the headlines. O. was prosecuted by the Public Prosecution Service for killing an Iraqi man during his deployment. ‘I saw what that case did to the service personnel around me. It was all anyone talked about. The case made soldiers anxious about using their weapons at all, because they feared they would immediately be prosecuted by someone in a wig and gown.’ The case and its impact planted a seed in Van Hoek’s mind. How is oversight of military use of force organised in legal terms, and what does international law require of the Dutch State? During his own deployments as a military lawyer, this was not clear. ‘We do have an oversight system, but how does it relate to international law?’ His doctoral thesis seeks to provide a sharper answer.

What constitutes lawful use of force by Dutch service personnel?

‘Service personnel must comply with the use of force instructions issued for their mission. These are commonly referred to as the Rules of Engagement. They are given a set of rules, and if they comply with them, the use of force is lawful. Naturally, the force must be used within the scope of the mission; it must be connected to the performance of their duties. Powers to use force are therefore tailored to each mission. The powers of our service personnel in Afghanistan differed from those in Iraq or in the Somali Basin (a submarine basin in the Indian Ocean, east of Somalia). But force is never an end in itself. It is solely a means of achieving a military objective. If that objective can be achieved in another way, that is what we do.’

What happens if the Rules of Engagement are not complied with?

‘If the Rules of Engagement are not complied with, this may constitute a criminal offence and trigger criminal proceedings. I do not address that situation in my thesis. I focus on circumstances in which there is, as yet, no reason to doubt the lawfulness of the use of force. Take the air strike on the bomb factory in Hawija. It was a planned operation, but the explosion proved far larger than anticipated, resulting in a significant number of civilian casualties. Both the Ministry of Defence and the Public Prosecution Service investigated how this could have happened. That is important because one naturally wishes to prevent it from happening again. It is also necessary to ascertain whether the rules were complied with. Within the armed forces, a report is routinely drawn up after the use of force. The Chief of Defence is informed, as is the Public Prosecution Service. The Public Prosecution Service is entirely independent of the defence organisation, so an independent authority looks over its shoulder. That is a positive feature, as it contributes to the legitimacy of military operations. The Netherlands is fairly unique in this respect. The question, however, is whether the Public Prosecution Service should always play this role. In my thesis, I examine the legal basis for use of force reports and the investigations that may follow.’

Is there a legal basis for investigating military use of force?

‘Under international humanitarian law and human rights law, the State is obliged to exercise oversight over the lawfulness of the use of force by service personnel. Reporting on the use of force is not a strict legal obligation, but in both fields of law, it is regarded as an important instrument for enabling effective oversight. When it comes to investigations, however, there is a clear difference. Human rights law proceeds from the premise that force may not be used unless it is absolutely necessary and requires that, following every instance of force, it be investigated whether it was lawful. International humanitarian law is less stringent. This is because it takes as its starting point that, during an armed conflict, force will be used; force is a given, albeit subject to rules. The law of armed conflict, therefore, does not compel an investigation into every instance of force. Ultimately, international law does not prescribe a single, uniform investigative procedure, nor does it require a State to assign investigations to one particular authority. As our system is currently organised, it is unclear within which legal framework an investigation is conducted: that of international humanitarian law or of human rights law.’

Why does that distinction need to be clear?

‘Within our oversight system, two branches of government have a role: the Ministry of Defence and the Public Prosecution Service. I argue that the Public Prosecution Service should step back where force has been used in an armed conflict during hostilities. Where there is no immediate suspicion of a breach of the Rules of Engagement, primary responsibility should lie with the Ministry of Defence. That is not to say that the Public Prosecution Service should never be involved. Where force is used outside an armed conflict, for example, during an anti-piracy operation on the high seas, the Public Prosecution Service should take the lead and the Ministry of Defence should step back. The legal framework that best fits the situation – in this case, international humanitarian law or human rights law – should determine the investigative procedures. I am concerned that outsiders may develop unrealistic expectations as a result of the way matters are currently arranged.’

What unrealistic expectations might arise?

‘In practice, an investigation is always conducted when civilian casualties result from military use of force. The current procedures are designed to ensure that this happens. That is not wrong in itself – quite the contrary – but I consider it important that everyone understands that, for example, the fact-finding investigation carried out by the Public Prosecution Service is not necessarily based on a strict legal obligation, but rather on a policy choice. It is important to explain that this is a policy choice which may change depending on the nature of the military operation. The current standard – that the Public Prosecution Service investigates every deployment of weapons involving civilian casualties – would not be sustainable if we were to become involved in a large-scale war. From a legal perspective, nor is it required.’

Why is the current approach not sustainable?

‘Suppose the Netherlands were to become involved in a large-scale conflict and have to fight on Europe’s eastern border. In that scenario, a great deal of force would be used, and there would likely be many casualties on both sides. In such circumstances, one operates within the framework of the law of armed conflict, and procedures must be organised accordingly. The current approach, with the extensive involvement of the Public Prosecution Service, would no longer be effective. Yet the role of the Public Prosecution Service in such a situation is not laid down anywhere. At the same time, it would also be possible to stipulate that the human rights framework should take precedence in other circumstances – for example, where a unit is stationed in a relatively stable environment and uses force at a checkpoint. I envisage that, in a wartime scenario, the Ministry of Defence would lead the investigation, with the Public Prosecution Service looking over its shoulder. Where human rights law takes precedence, the role of the Public Prosecution Service would become more prominent. It is important that we also view these procedures through a legal lens. I find it striking that legislation clearly regulates when Dutch service personnel may be deployed and which powers to use force they are granted, yet oversight of the exercise of those powers is relegated to policy documents.’