In general, if we define the principle of equal treatment of parties in the stages of arbitration, we can not speak of an equality with exact boundaries in the mathematical sense. The important thing is to treat similar situations in a similar way. As it is known, each situation has its own specific factors, and we cannot draw sharp boundaries while realizing the principle of equal treatment of parties.
The fundamental principle in the principle of equal treatment, which includes treating different situations differently, is to provide equal opportunities for the parties to access justice. The equal treatment of evidence presentation rights of the parties in the stages of litigation is also a consequence of the principle of equality of arms. The equality of arms, in civil law, means providing the opportunity to present their claim, defense, and evidence for both sides so that neither side is in a weak position against the other.
The principle of equal treatment of parties also includes elements such as access to an impartial court, fair trial, timely conclusion of the trial, publicity in the trial, and a decision in accordance with justice. It should not be forgotten that the parties deserve a fair decision according to their situations in the dispute.
The principle of equal treatment of parties is one of the most important principles in international arbitration proceedings, and it must be applied. Equal treatment of parties is necessary for the fair evaluation of the claims of the parties and for the fair decision. During the litigation process, the principle of equal treatment of parties must be observed in the provision of the right to claim and defense, and no party should be put in an advantageous position over the other.
If the principle of equal treatment is not followed, it cannot be said that the right to claim and defense is respected. For example, in cases where a claim belonging to one of the parties that was put forward in a timely manner and related to the dispute is ignored, not only the principle of equality but also the violation of the right to claim and defense will occur.
Article 18 of the UNCITRAL Model Law states that "The parties shall be treated equally and each party shall be given a full opportunity of presenting his case."
For example, the failure to grant the right to submit a rejoinder to one of the parties in an international arbitration dispute also constitutes a violation of the principle of equality. Local court decisions rejecting the enforcement of arbitral awards in such cases exist.
Under Article 22 of the ICC Arbitration Rules d in 2017 (Article 15(2) of the ICC Arbitration Rules dated 1998), the arbitral tribunal always acts fairly and impartially and provides sufficient opportunities for the parties to present their claims and defenses.
While observing the principle of equal treatment of parties, it should not be forgotten that the procedural rules used in arbitration must be applied regardless of which country's legislation or in what way they are chosen. In other words, regardless of the chosen procedural rules, arbitrators should treat parties equally and respect the right to claim and defense. The parties can only waive the principle of equal treatment of parties voluntarily, but it cannot be waived by the arbitrator.