An individual (or separate) opinion is an opinion that is submitted in circumstances where an arbitrator (or a judge) wishes to express a dissenting or assenting point of view.¹ An individual opinion can either relate to the decision of the panel in its entirety or to just one -or more parts of it. 

Arbitrators may submit dissenting opinions when they disagree with the outcome of the case reached by the tribunal. In other cases, arbitrators may agree with the decision in general but have a different opinion on certain points (such as the legal basis for reaching a certain conclusion): in these circumstances, they may reveal these differences in a concurring (assenting) opinion.² Concurring opinions can either be short³ or comprise a detailed⁴ description on points of disagreement or on points where the arbitrator wants to supplement⁵ the considerations of the tribunal.

Individual opinions can be distinguished from simple “statements of dissent” or a “declaration” which reflects a shorter clarification addressing a limited number of points relating to the case.⁶

1. Dissenting Opinions
2. Concurring (assenting) Opinions

It is notable that most arbitration rules (including such rules as ICC, LCIA or UNCITRAL) do not contain any provisions regulating individual opinions of arbitrators.⁷

However, Article 48(4) of the ICSID Convention and Article 47(3) of the ICSID Arbitration Rules allow individual opinions to be submitted. Similar provisions can also be found in Article 57 of the Statute of International Court of Justice, Article 30(3) of the Statute of the International Tribunal for the Law of the Sea, Articles 14(3) and 17(11) of WTO’s Dispute Settlement Understanding.

Individual opinions can open new discourses around certain issues of law, as well as re-examining older ones. In this way, individual opinions create a broader reasoned framework within which the development and interpretation of international investment law can take place. For example, where an individual opinion explores new or difficult issues of law, future tribunals may consider or rely on such reasoning when rendering a decision (even if the point under discussion was not determinative - or was a dissenting opinion - in the context of the original award).⁸ 

Dissenting opinions criticizing the final decision of the arbitral tribunal may also point out downsides of the award. These can subsequently serve as a roadmap for any subsequent ad hoc committee constituted for the purpose of annulment proceedings. One of the most flagrant cases of annulment of arbitral awards with the reference to an individual opinion was Occidental Petroleum v. Ecuador.⁹

In accordance with Article 48(4) of the ICSID Convention, individual opinions are rendered within the final award. However, nothing in the ICSID Convention or ICSID Arbitration Rules prohibits to file an individual opinion to other decisions of the tribunal such as the decisions on jurisdiction, provisional measures, or partial awards.¹⁰

Individual opinions are usually drafted after the final award is produced. In this way, the dissenting or concurring opinion can be based on the unanimous reasoning advanced by the tribunal.¹¹

Fouret, J., Gerbay, R. and Alvarez, G.M., The ICSID Convention, Regulations and Rules: A Practical Commentary, Edward Elgar Publishing, 2019.

Schreuer, C., Malintoppi, L., Reinisch, A. and Sinclair A., The ICSID Convention: A Commentary, Cambridge University Press, 2nd ed., 2009.

Breeze, R., Dissenting and Concurring Opinions in International Investment Arbitration: How the Arbitrators Frame Their Need to Differ, International Journal for the Semiotics of Law – Revue Internationale de Sémiotique Juridique 25(3), 2012.

Breeze, R., Balancing neutrality and partiality in arbitration: discursive tensions in separate opinions, Text & Talk, Vol. 36, Issue 4, 2016.

Charlotin, D., A Data Analysis of the Iran–US Claims Tribunal’s Jurisprudence—Lessons for International Dispute-Settlement Today, Journal of International Dispute Settlement, Vol. 10, Issue 3, September 2019.

Titi, C., Investment Arbitration and the Controverted Right of the Arbitrator to Issue a Separate or Dissenting Opinion, The Law & Practice of International Courts and Tribunals, Vol. 17, Issue 1, 2018.