An arbitration brought by Omani investor Petrogas E&P against the Netherlands, first revealed in November 2025, took clearer shape in 2026. According to a ministerial letter sent to the Dutch Parliament on May 18, 2026, Petrogas requested arbitration on May 28, 2025 under the Netherlands-Oman BIT, alleging that the temporary solidarity contribution levied on 2022 windfall profits, implementing EU Regulation 2022/1854, and the temporary increase of royalties under the Mining Act for 2023 and 2024 breach the treaty. The tribunal has been constituted and adopted its first procedural order on March 29, 2026; the case proceeds under the 2010 UNCITRAL Rules with the Permanent Court of Arbitration administering (PCA Case No. 2025-47). Civil society groups have condemned the claim as an attack on crisis-response taxation. It is at least the third pending ISDS case against the Netherlands, alongside the Groningen claims, and parallels the Klesch arbitrations against Germany, Denmark, and the EU over the same levy, confirming windfall taxation as a new front in investor-state litigation.