International law is comprised of different aspects such as treaties, charters (for example the UN Charter), protocols, international agreements, customs and legal precedents (Wet 2002). Traditionally, international law was concerned with governing of relationship between states. Yet, the law has undergone considerable evolution over the years to include relations between international organisations’, individuals and states. This has greatly broadened the international law. International law plays an essential role in solving global concerns/issues affecting different facets of humanity such as insecurity. Focarelli (2012) supports the view that international law can enhance promotion of global justice if it is considered as a social phenomenon. One of the fundamental responsibilities of the state is to ensure security in the society. According to Ruka (2017), individual states and the international community have duties and responsibilities that they are required to fulfil under the substantive and formative law amongst them promoting security in the society. Thus, the state is linked to international law. Unlike domestic/national law, implementation of international law by states is voluntary (Janzekovic & Silander 2014). States are required to accept the commitments stipulated under the international treaty to be bound by such commitments. The voluntary nature of international law has considerable implications on the extent to which states may follow the international treaties. Childress (2011) emphasise that the lack of central enforcement under international law means that states must be motivated to comply by other factors rather than the threat of facing internal sanctions. This indicates that international law may be characterised by challenges in shaping state behaviour. This research paper evaluates the extent to which international law shapes state behaviour with reference to the UN Charter and international law governing the use of force. The analysis evaluates the circumstances and extent to which international law either prohibits or allows states to use force. Analysis International law and state behaviourIn international law, the phrase state behaviour is used to refer to how a country’s domestic behaviour is influenced or altered by the goals and objectives of stipulated by international institutions or treaty obligations (Withana 2008). To promote global peace following occurrence of World War I and II, the United Nations formulated a Charter whose goal was to cut the use of armed force in dealing with conflicts between states. Article 2(4) of the Charter prohibits UN member states from threatening or resorting to use of force against another politically independent state or threatening its territorial integrity or acting in a manner that is contrary to the purposes of the UN (Joyner 2005; Arend & Beck 2014). In spite of these requirements, there are grounds on which the UN Charter allows states to resort to use of force as expounded herein. Self-defence States’ involvement in transnational intervention is considered violation of another country’s territorial integrity and national independence (Withana 2008). States may only be permitted to resort to force as self-defence. A state has a right to self-defence and hence may take that action by itself. Or, a state may seek help of another state. An attack on one of UN member states may compel other states to respond by attacking the aggressor (Reus-Smit 2004). For example, according to Article 5 of the North Atlantic Treaty, an attack on a member state is considered an attack on all the NATO member states. Under such circumstances, the member states are obliged to attack. This indicates that international law may compel states to act collectively in response to use of force. A decision to use force in self-defence must however be authorised by the UN Security Council under Chapter 7 of the UN Charter (Withana 2008). In granting a state the right to use force in self-defence, the UN Security Council evaluates whether the situation faced poses a breach of a state’s peace, threatens peace or is an act of aggression. The Security Council’s goal in granting a state permission to use force is to enhance restoration and maintenance of international security and peace (Focarelli 2012). This indicates that the UN Charter, which forms a key component of international law, advocates for states to adopt the state of non-intervention unless a decision to resort to force is ratified by the UN Security Council (Mgbeoji 2003). Through this approach, international law has been successful in shaping state’s behaviour by restricting them from resorting to use of force or acting violently towards other states in their international relations. If a state resorts to use of force against another state under the principle of self-defence, the particular state must prove many elements in order to its actions not to amount to an illegality under the international law. The state must prove that its decision to use force was a necessity of self-defence. A state can prove necessity of self-defence by illustrating that its decision to use force was as a result of a looming armed attack by another state. Therefore, a state cannot rely on economic reasons in using force against another state (Scott, Billingsley & Michaelsen 2010). In the event of an imminent armed attack, the state may not necessarily use force against another country but also an organisation. This assertion is showed in the 1976 case of Israel and Uganda in which Israel commandos conducted an armed raid on Entebbe Airport in an effort to save many Israeli nationals taken hostage by a Palestinian terrorist group. Israel’s justification in using force in another state was because the Ugandan government was either unable or unwilling to respond in saving the Israel nationals (Aust 2010). Article 51 of the UN Charter allows states to resort to use of force in the event of terrorist attack. In light of this, international law provides states the capacity to respond to security threats posed by not only states but also non-state actors such as terrorist groups. The rationale of the concept of imminent attack is to enable a country pre-empt such an attack.The action to use force should have been instant and did not leave choice of means. In proving that the use of force of necessary, a state must show that there was no any other workable option under the circumstances faced (Tsagourias & Buchan 2015).The state should also prove that there was no time for deliberations. Moreover, the state must also prove that its application of force in self-defence was not unreasonable or excessive because the actions were limited by the need for self-defence and hence limited to that (Gross & Aolain 2001).On the basis of this, states are required to ensure that their behaviour in the event of self-defence is proportionate. Subsequently, if states consider using force as self-defence, they must refrain from applying force that is more than what is necessary in repelling an act of aggression, breach of or threat to its nation peace. Disproportionate use of force in situations of self-defence is illegal under international law (Malanczuck 2002). This aspect is underlined in the 1987 and 1988 case in which the US launched an attack on Iranian oil platforms in response to Iran’s attack on the US and a number of its ships with mines and missiles. Besides attacking the Iranian oil platforms, the US also sank two Iranian frigates, naval vessels and destroyed Iranian aircrafts. In response to US actions, the International Court of Justice ruled that US’s actions were disproportionate in enacting its right to self-defence (Solis 2010). In case of self-defence, the UN Charter specifically requires states to ensure that force is specifically restricted for the instant purpose. Thus, states are prohibited from resorting to use of force for purposes of punitive attack, reprisals or retribution (Aust 2010). If a state uses force contrary to the UN Charter, sanctions may be used against such a country. The use of such strategy has greatly enabled countries to refrain from using force in their international relations. This underlines that international law influences how states should behave in resorting to use of force as an approach to self-defence.Enforcement action Under the UN Charter, the Security Council has the power to compel states to use force on its behalf as an enforcement action. This situation may occur if the Security Council, which is charged with the responsibility of maintaining international security and peace, determines that attainment of this goal as stipulated by Article 39 of the UN Charter is under threat or has been breached. In its legal capacity, the Security Council may direct its member states to use force in assisting a state under threat to quash the threat. Through this approach, the Security Council is able to assist states undertake their responsibility hence improving its success in promoting international peace and security (Abass 2012). For example, in 1990, the Security Council compelled states led by the US to apply ‘all necessary means’ to liberate Kuwait from an attack and subsequent occupation by Iraq (Aust 2010). Therefore, a resolution based on the UN Charter can allow states to either individually or collectively apply armed force against another state that violated peace and security or a non-state actor operating within the jurisdiction of another state. Thus, states may be required to use force as a matter of obligation. Through this approach, the UN Charter on use of force is able to influence states’ behaviour. Humanitarian intervention In addition to the exception on use of force on ground of self-defence and as an enforcement action, states may also be required to use force on humanitarian grounds. Humanitarian intervention is an important subset of international law that governs the use of force. According to Zaid (2013), humanitarian intervention ‘occupies an institutional position alongside security authorisation and self-defence as a legitimate and legal reason for war’ (p.1). In spite of the fact that the UN Charter is not explicit on the use of force in response to humanitarian issues, the UN Security Council may authorise use of force such as military intervention against other sovereign states in an effort to safeguard the livelihood of people and societies that might be threatened by the actions of the state (Aust 2010). This aspect is underlined on the concept of responsibility to protect, which stipulates that the international community is obliged to offer assistance to a state that which has failed to protect its citizens or is involved in acts of repression on its population. Under such circumstances, use of force is considered necessary as a measure of last resort (Abass 2012). The capacity to international law in influencing states to resort to use of force on ground of humanitarian intervention is well illustrated in the case of 1991 military intervention by British, US and French forces in Iraq. The military intervention was ratified under Resolution 678 (1990) of Chapter VII (Wet 2002). The objective of the military intervention was to offer protection to thousands of Kurds in Northern Iraq who were faced by a serious security threat from the Iraq government forces. The livelihood of thousands of Kurds was threatened through as a result of internal displacement and subsequently faced a serious humanitarian problem because of lack of basic necessities such as water, food, shelter and medicine. Failure to provide the affected communities could have resulted in thousands of deaths. However, the Iraq forces restricted humanitarian agencies from accessing the affected communities (Aust 2010).In response to the situation, the UN Security Council approached the entry of the US, UK and French military forces in order to create an environment for humanitarian aid workers to provide the basic necessities to the affected (Aust 2010). However, considering the use of force by the Iraq forces in an effort to bar the foreign military forces from operating in the affected region, the French, British and American forces resorted to use of force in spite of the fact that it was not approved by the UN Security Council on the ground that such an approach would have increased human casualties. Nevertheless, the UK, US and French governments proved that the use of force in the military intervention was necessary in dealing with such a matter involving extreme human distress. This underlines the fact that the UN Charter is not rigid in controlling states approach to use force against another state if the use of force is justifiable on humanitarian ground (Davidson 2013). Conclusion This essay confirms that international law with reference to the UN Charter governing the use of force greatly influences and shapes state behaviour. In spite of the fact that the Charter prohibits use of force in international relations, there are exceptions on which states may be permitted to use force. One of the grounds relate to cases of self-defence in which a country may apply force in an effort to protect its national sovereignty. However, states are required to ensure that use of force is proportionate and necessary. States may also be required to use force by the UN Security Council in undertaking an enforcement action under the responsibility of the UN Security Council to promote international peace and security. Alternatively, states may also legally use force in cases of humanitarian intervention. In summary, these aspects highlight that international law significantly impacts how states behave in response to promotion of domestic and international peace and security. Thus, the international law on use of force under the UN Charter is flexible which improves its effectiveness in promoting international peace and security.