The dispute, brought by UK-based South32 SA Investments Limited against the Republic of Colombia, arose under the 2010 United Kingdom-Colombia Bilateral Investment Treaty. It concerned a series of measures taken by Colombian state entities, primarily the National Mining Agency (ANM) and the Comptroller General (Contraloría), that retroactively recalculated and demanded additional mining royalties from the Claimant's local subsidiary, Cerro Matoso S.A. (CMSA), which operates the Cerro Matoso nickel mine under long-standing concession contracts. The measures challenged by the Claimant fundamentally altered the basis for royalty calculations that had been in place for decades. The Claimant argued that these measures, which spanned four main areas, collectively violated the Fair and Equitable Treatment (FET) standard under Article II.3 of the BIT. The first area involved Colombia's decision to retroactively apply a higher royalty rate (12% instead of 8%) and a lower cost-deduction percentage to periods before the concession contracts were legally considered renewed. Second, the Claimant contested the retroactive application of a new methodology for calculating the reference price of nickel, established in 2015 via Resolution 293. Third, it challenged the disallowance of various costs that CMSA had deducted for decades, with the authorities alleging a lack of direct causal link to the mining operation, often for historical periods where CMSA was no longer legally required to retain supporting documentation. Finally, the Claimant disputed Colombia's unprecedented demand for royalties on the iron content of the ferronickel produced, in addition to the long-standing royalty on its nickel content. Colombia raised several jurisdictional objections, all of which were dismissed by the Tribunal. It argued that South32 had engaged in treaty shopping by restructuring its investment to gain access to the BIT's protections; the Tribunal found the investment was protected by a UK entity both before and after the corporate restructuring, thus no abuse had occurred. Colombia also contended the dispute was purely contractual and domestic, but the Tribunal affirmed its jurisdiction to assess whether the state's conduct, while rooted in domestic law, amounted to a breach of international law under the BIT. On the merits, the Tribunal unanimously found that Colombia had breached the FET standard. It concluded that the state's conduct, viewed cumulatively, was arbitrary, contradictory, non-transparent, and violated the investor's legitimate expectations and legal security. The Tribunal highlighted the state’s inconsistent behavior, where it contradicted its own long-standing practices and prior administrative decisions without reasonable justification. The retroactive application of new rules was found to be a key element of this breach, creating profound legal uncertainty. The actions of the Contraloría, in particular, were deemed abusive and a violation of due process, especially in demanding evidence for costs from decades prior. The demand for royalties on iron was characterized as an abusive double-gravamen, as the iron did not add value to the ferronickel, which was already taxed for its nickel content. As a result, the Tribunal awarded South32 USD 4,519,417 in compensation for historical damages, representing overpayments for disallowed costs and royalties on iron. However, a majority of the Tribunal rejected the claim for damages related to the new reference price methodology. In a significant but contentious remedy, the majority ordered Colombia to indemnify South32 for any future damages that may arise from the execution of the other measures found to be in breach of the treaty. The Claimant was also awarded USD 5,050,000 in costs. The decision was accompanied by a partial dissent from Arbitrator Guido Tawil, who disagreed with the majority's finding on the reference price methodology, and a full dissenting opinion from Arbitrator Andrés Jana Linetzky, who argued that awarding an indemnity for future, non-materialized damages was beyond the Tribunal's authority.