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One Lithium Project, Three Treaty Proceedings

  • Writer: Aişe Gül Akkoyun
    Aişe Gül Akkoyun
  • Jul 29
  • 3 min read

Updated: Aug 3

What Sonora tells us about consolidation, funding, and the future of mining disputes.

Background

Mexico's Sonora Lithium Project has become one of the more closely watched flashpoints in critical-minerals arbitration. The dispute traces back to the cancellation of the mining concessions that underpinned the project, which is why lithium, the mineral at the centre of electric-vehicle battery supply chains, sits at the heart of this story. What makes Sonora unusual is not the underlying grievance itself, but the fact that it has produced not one but three separate ICSID proceedings.

Three cases, one project

Different investors, through different corporate vehicles incorporated in different jurisdictions, came to hold different interests in the same underlying project over time. Since treaty protection runs through nationality, each investor group can only invoke the treaty tied to its own corporate nationality. That is why one project has produced three separate proceedings rather than one:

  • Bacanora Lithium, Sonora Lithium and Ganfeng v. Mexico (ICSID Case No. ARB/24/21), British and Chinese claimants, invoking both the UK-Mexico and China-Mexico BITs over seven of the project's mining concessions.

  • Estate of Ian Colin Orr-Ewing and others v. Mexico (ICSID Case No. ARB/25/30), a British claimant group with separate interests in the same concessions.

  • Cadence Minerals and REM Mexico v. Mexico (ICSID Case No. ARB/26/36), registered recently, British claimants asserting a 30 per cent interest, with the claim financed by a third-party litigation funder rather than out of pocket.

Why consolidation is contested

Three related claims raise an obvious institutional question: should they be heard together? Mexico has pressed for exactly that, filing a request in September 2025 to consolidate the first two proceedings under Article 14 of the UK-Mexico BIT, a treaty mechanism that allows a specially constituted tribunal to take over related claims where joint resolution would be fair and efficient. A separate Consolidation Tribunal was duly constituted in November 2025 and the question remains pending. Meanwhile, the underlying ARB/24/21 tribunal has already had to navigate its own procedural turbulence, including a rejected request to bifurcate the case and a change in the tribunal's composition following an arbitrator's resignation in 2026.

What the pattern reveals

Taken together, the three Sonora proceedings offer an unusually well-documented case study. Not because the underlying legal situation is simple (it isn't), but because, unlike in most disputes, none of the key variables here are hidden. We know exactly how many proceedings exist, which treaties each one invokes, that a consolidation request has been filed, and that a funding arrangement stands publicly disclosed.

Third-party funding, in particular, is rarely this visible. In Muhammet Cap and Sehil v. Turkmenistan (ICSID Case No. ARB/12/6), it took over a year and a contested tribunal order before a funding arrangement was even confirmed to exist. Sonora skips that fight entirely, giving researchers a rare and largely complete picture of how ownership in a single resource project fragments across corporate vehicles and nationalities, and how treaty protection fragments along with it, leaving each investor group to pursue its own forum under its own treaty.

The open question

Sonora leaves regulators, tribunals and investors alike with an unresolved tension: should consolidation follow the economic reality of a single underlying project, treating fragmented ownership as one dispute in substance, or should the separate legal identity and treaty-specific consent of each investor remain decisive, even at the cost of parallel and potentially inconsistent proceedings?


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