The Main Source of International Law and Change in their Relative Importance since World War II

Introduction
International law is a set of universal rules and principles that governs the relations between states and international organization as well as the relationships between sovereign states (Shaw, 2008). However, this law has a jurisdiction over the non-state actors such as corporations, individuals, armed militia, rebels and groups seeking to break away from states among others (Shaw, 2008). International law deals
with matters such as military issues, diplomatic relations, and the territorial issues within states (Atapattu, 2009). The efficiency of the law derives from the control that is exercised by individual states that develop the law (Shaw, 2008). At the centre of success of the international laws, lies the consent by the states that adopt it. There is no common parliament that can make the international law making it to have a variety of sources. There are four major sources of law as recorded in the Article 38 of the international criminal justice. They include international treaties and conventions, customary law, general principles law and the subsidiary sources. This paper explores the sources and examines whether or not they have changed since the World War II.
Sources of International Law
Treaties and Conventions
International conventions or treaties have the capacity of either being multilateral or bilateral (Aspremont, 2011). Treaties have different names such as pact, memorandum of understanding, and exchange of letters among others and is document and refers to a written legal document that is agreed upon between sovereign states (Thirlway, 2014). It is the most common source of law that deals with a plethora of matters (Aspremont, 2011). Large multilateral treaties often codify certain fields like diplomatic relations laws and the laws of the sea, engaging the attention of those dealing with the development of international law. Some treaties have been so successful in institutionalizing international law in the respective states (Thirlway, 2014). One example of such a successful treaty is the Vienna Convention on the Law of treaties that came into force on 27th January 1980 (Thirlway, 2014). This treaty despite not being the complete code of law of treaties, give a declaration on existing laws and has a command on the participation and acceptance at universal level. Bilateral treaties serve as useful instruments in the law making process. Certain areas of international law are regulated via these kind of treaties. A good example is the extradition treaties, bilateral investment agreements, and air transport treaties.
Customary Laws
Customary laws is one of the traditional sources of international law together with treaties (Thirlway, 2014). It is more common on the international rather than domestic legal systems. Because international law fails to develop an efficient codified method of law making, the patterns and behaviours among states forms the source of law from where international law derives (Thirlway, 2014; Atapattu, 2009). The patterns of behaviours are referred to as practice (Murphy, 2012). When the practice is based upon a legal obligation, it is considered a customary international law (Aspremont, 2011). Owing to the fact that international customary law is an ongoing process, it is flexible compared to treaties (Murphy, 2012). A clash between treaties and customs lead to complex situations.
General Principles of Law
These are a source of international law that are theoretically similar or equivalent to customary law and treaty. However, practically they are used to close the gaps existing between treaties and customary law (Thirlway, 2014). Their establishment is form a comparison of the national legal systems in the world (Dixon, 2013). When there is consistency or commonness of the principles of most of the legal system, the principle are adopted as international law (Dixon, 2013). Explicit examples of general principle law include the protection of acquired rights and principles that govern procedural fairness before the court (Thirlway, 2014). General principles of law have been useful and have since received applications more so in the arbitral tribunals (Aspremont, 2011). Being that there is a wide coverage of international legal systems, representative legal systems from civil law, common law and Islamic law and other different legal cultures are studied to publish the general principle laws in a language that is accessible (Aspremont, 2011).
Judicial Decisions and Writings of Publicist and Jurist
Judicial decisions are referred to a subsidiary means that aid in the determination of rule of law (Aspremont, 2011). The decisions of courts is only binding to the parties to the case to which decision is given (Thirlway, 2014). With respect to this, international law can be developed and advanced from a complete scrutiny and therefore reference of the decisions previously made by courts; either national or international, and arbitral tribunals (Thirlway, 2014). Various professionals are therefore able to transform and advice the parties to the legal proceedings or act as consultants in the development of the law (Murphy, 2012).
The decisions previously made by the ICJ has been very significant and influential in the development of international law (Murphy, 2012). A good example that is referenced most is the reparations case that later established the legal personality of the United Nations. The writings or literature by jurists and publicists play an integral role in the development of international law (Murphy, 2012). These writings inform the continuous process of developing as well as refining international law. In this context, the writings inform the decisions made by governments thus informing the state practice. Resolutions by expert bodies also fall under this category.
Despite the changes that are experienced globally, the relative importance of the sources of international law has not changed since the World War II (Thirlway, 2014). This is due to the mere fact that there is a coexisting dependence of the sources of international law (Rayfuse & Scott, 2012). Put simply, one source of the law needs another so as to ensure a coherent implementation of justice internationally (Thirlway, 2014). The continuous development of international law is attributed to the above mentioned sources in alignment with the developmental pace of the world. Being that in the 20th century most of the states have achieved greater international cooperation, international law still continues to be refined from the changes that are taking place in the platforms where the sources are based (Thirlway, 2014; Rayfuse & Scott, 2012). There is difficulty in forging a new source owing to the clarity, completeness and exhaustiveness of the statute by ICJ in Article 38 (Thirlway, 2014). This therefore defends the fact that the importance of the sources still remains integral in the development and further refinement of international law.
Conclusion
There are four major sources of international law. These include treaties and conventions, customary international law, general principles law and the decisions by courts and tribunals as well as writings by jurists and publicists as discussed in this paper. It is evident that the Article 38 set a pace for the components that warrant being sources of international law. As have been seen, despite the changes in the world since the Second World War, the relative importance of the sources of international law still remains unchanged. This can be attributed to the fact that the Article 38 by the ICJ was very clear, exhaustive and complete in nature. This also explains the reason why despite the rapid change being experienced, no new source of international can be adopted. It is noteworthy that the interdependence between the sources further makes it even more difficult to discredit the relative importance of a source.

References
Aspermont, J. (2011). Formalism and the sources of international law: A theory of the ascertainment of legal rules. Oxford: Oxford University Press.
Atapattu, S. A. (2009). Emerging principles of international environmental law. Ardsley, NY: Transnational Publishers.
Dixon, M. (2013). Textbook on international law. Oxford: Oxford University Press.
Murphy, S. D. (2012). Principles of international law. St. Paul, MN: Thomson/West.
Rayfuse, R. G., & Scott, S. V. (2012). International law in the era of climate change. Cheltenham, U.K: E. Elgar.
Shaw, M. N. (2008). International Law. Leiden: Cambridge University Press.
Thirlway, H. W. (2014). The sources of international law. Oxford: Oxford University Press.