The Clash between Treaty Law and Customary International Law

Introduction

The clash between treaty law and customary international law is a complex issue that arises in the field of international law. Treaty law refers to the binding agreements between two or more states, while customary international law is a set of unwritten rules and practices that are considered legally binding on all states.

The fundamental principle of treaty law is pacta sunt servanda, which means that agreements must be upheld. This principle is also enshrined in the Vienna Convention on the Law of Treaties, which states that "every treaty in force is binding upon the parties to it and must be performed by them in good faith." However, the problem arises when there is a conflict between treaty law and customary international law.

Customary international law is a source of law that is derived from the consistent and widespread practice of states. It is generally considered to be legally binding on all states, regardless of whether they have ratified a particular treaty. For example, the prohibition on torture is part of customary international law, even though it is also enshrined in the Convention against Torture.

Difference

The conflict between treaty law and customary international law arises because treaties are binding only on the parties to them, while customary international law is binding on all states. If a state has ratified a treaty that conflicts with a customary international law norm, it may find itself in a difficult position. On the one hand, it is bound by the terms of the treaty, but on the other hand, it is also bound by customary international law.

One perspective is that treaty law should always take precedence over customary international law because treaties are formal and binding agreements between states. Proponents of this view argue that treaty law is more specific and precise than customary international law, making it more appropriate to apply in cases of conflict.

However, others argue that customary international law should take precedence over treaty law in situations where the two conflict. Proponents of this view argue that customary international law reflects the consensus of the international

community, and as such, it should be given greater weight than the obligations of individual states under a treaty.

One of the most significant clashes between treaty law and customary international law has occurred in human rights. Many states have ratified human rights treaties, such as the International Covenant on Civil and Political Rights and the Convention on the Rights of the Child. However, there are also many human rights norms that are part of customary international law, such as the prohibition on torture and the right to a fair trial.

The clash between treaty law and customary international law has also been evident in the context of the United Nations Security Council (UNSC). The UNSC has the power to adopt binding resolutions under Chapter VII of the UN Charter, which are binding on all UN member states. However, these resolutions can also conflict with customary international law, particularly in human rights.

Analysis 

The clash between treaty law and customary international law raises important questions about the hierarchy of sources of international law. Should treaty law always prevail over customary international law, or should the two be given equal weight? There is no easy answer to this question, as it depends on the specific circumstances of each case.

One possible solution to the clash between treaty law and customary international law is to give greater weight to customary international law. This would require states to ensure that their treaties are consistent with customary international law norms, and that they do not undermine or weaken existing customary international law norms.

Another possible solution is to develop a more comprehensive and coherent system of international law, which considers both treaty law and customary international law. This would require greater cooperation and coordination among states, as well as a greater willingness to engage in dialogue and compromise.

Some case examples of the Clash

Asylum Case (Colombia v. Peru), 1950:

In this case, the International Court of Justice (ICJ) had to determine whether the right to grant asylum, as established under customary international law, could be limited by a treaty. Colombia argued that the 1934 Treaty of Lima between Colombia and Peru did not preclude Colombia from granting asylum to Peruvians, but Peru argued that the treaty overrode customary international law. The ICJ ultimately held that the treaty did not abrogate Colombia's right to grant asylum, and that customary international law continued to apply.

Gabčíkovo-Nagymaros Project Case (Hungary v. Slovakia), 1997:

In this case, the ICJ had to determine the relationship between the 1977 Treaty on the Construction and Operation of the Gabčíkovo-Nagymaros System and customary international law. Hungary argued that Slovakia's unilateral suspension of the project violated both the treaty and customary international law, while Slovakia argued that the treaty should prevail over customary international law. The ICJ ultimately held that the treaty did not entirely replace customary international law, and that Slovakia's actions were in breach of both.

Case Concerning Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Bosnia and Herzegovina v. Serbia and Montenegro), 2007:

In this case, the ICJ had to determine whether the Genocide Convention's prohibition on genocide had become part of customary international law. Bosnia and Herzegovina argued that Serbia and Montenegro had committed genocide against Bosnian Muslims during the Bosnian War, while Serbia and Montenegro argued that the Genocide Convention only applied to treaty parties. The ICJ ultimately held that the prohibition on genocide had become part of customary international law, and that Serbia and Montenegro had violated this law.

These cases demonstrate the complexity of the relationship between treaty law and customary international law, and the challenges of reconciling the two.

Conclusion

In conclusion, both treaty law and customary international law are respected sources of international law and carry equal weight in terms of their legal authority. Neither is considered to precede the other in terms of their legal standing. The clash between treaty law and customary international law is a complex issue that requires careful consideration and analysis. While there is no easy solution to this problem, greater attention needs to be paid to the relationship between treaty law and customary international law, and to the need for a more comprehensive and coherent system of international law. Only through such efforts can we hope to resolve the tensions and conflicts that arise in the field of international law.

~Authored by Tanisha Dhariwal

Juris Doctor Candidate at University

of Sydney