The World Bank's International Centre for Settlement of Investment Disputes (ICSID) ruled against a claim for compensation related to El Salvador's denial of a mining license for the El Dorado gold-silver project.
The ICSID ordered Pac Rim Cayman to pay US$8.0mn in legal costs to El Salvador.
Melbourne-based OceanaGold said it was disappointed at the decision and planned to review the ruling before evaluating next steps for its El Salvador business unit.
El Dorado has a measured and indicated resource of 1.30Moz gold and 9.48Moz silver.
The ruling was described as a victory for the people of El Salvador by presidential spokesman Eugenio Chicas.