After trying some legal and political choices in order to settle the disputes with Uruguay about the treaty of 1975 Uruguay River statute, Argentina proceed against Uruguay before the ICJ. The allegations based on the procedural and substantial matters violations, set forth in the statute, and violation against some international environmental law principals which all of them related to potential risks arising from launching two paper mill located near the border river. After the time that the ICJ recognized its jurisdiction and initiating the trial and considering the petition, defenses and the evidences, finally, on 20th of March 2010, issued its second environmental judgment after the case of 1977, the dispute between Hungary and Slovakia. The court has mentioned many important matters of customary rules of international environmental law and some of its subjects such as prevention principals, environmental assessment and prevention of harmful activities. In this judgment, the court did not properly adjudge Uruguay’s violations of substantive obligation and adjudge Uruguay just for violations of procedural rules.