Below the Treaty: Investment Treaties, CBAM, and Climate-Aligned Investment Law in Türkiye

Türkiye is constructing a domestic climate architecture while remaining bound by investment treaty commitments concluded decades before climate policy assumed its present form. This working paper asks which legal techniques for reconciling the two are in fact open to an economy so situated. It argues that the regimes composing sustainable investment law are diverging rather than converging. Climate obligations have hardened through the 2025 ICJ advisory opinion and parallel rulings. Corporate disclosure has softened under Directive (EU) 2026/470 and the US reversal. Multilateral trade adjudication remains frozen. What binds third-country producers is now a priced condition of market access through the EU Carbon Border Adjustment Mechanism. In this setting, the balance between investment protection and climate regulation is struck below the multilateral treaty, in domestic investment legislation and individual investment contracts. Treating Türkiye as the critical case, the paper finds that treaty-level "doing no harm" reforms are largely out of reach for a state with a large legacy treaty stock and continuing Energy Charter Treaty membership, while the positive agenda, domestic law and contract design remain available. It proposes reforms at treaty, statutory and contractual level.