Separability: the arbitration agreement stands alone
Although it usually sits inside the main contract, the arbitration agreement is a distinct agreement. Under the separability doctrine (section 7 of the Arbitration Act 1996), it survives even if the main contract is void or terminated - and it can have its own governing law, separate from the law of the matrix contract.
That separate law matters: it decides whether the arbitration agreement is valid and binding, what disputes fall within it, and how ambiguous wording (for example, whether disputes arising under this contract reaches tortious claims) is construed.
The old default: Enka v Chubb
Until recently the position came from Enka Insaat Ve Sanayi AS v OOO Insurance Company Chubb [2020] UKSC 38. Where the parties had not chosen a law specifically for the arbitration agreement but had chosen a law for the main contract, that main-contract law was generally presumed to govern the arbitration agreement too, and choosing a different seat did not by itself displace that presumption.
That produced a trap: a main-contract law with stricter formal requirements could invalidate an arbitration agreement the parties plainly intended to work.
The new default: Arbitration Act 2025 section 6A
The Arbitration Act 2025 (in force 1 August 2025) reverses this. New section 6A provides that the arbitration agreement is governed by the law of the seat unless the parties expressly agree otherwise - and it makes clear that choosing a governing law for the main contract is not, by itself, an express choice for the arbitration agreement.
So for agreements entered into after August 2025, the default flips: absent an express choice, the seat's law governs the arbitration agreement. For an England-seated arbitration, that means English law, with its permissive approach to validity.
Why it changes outcomes
Consider a contract governed by a foreign law but seated in London. Under Enka, the arbitration agreement would generally have been governed by that foreign law - and if that law imposed formal requirements the clause did not meet, the arbitration agreement could fail. Under section 6A, the same clause is governed by English law by default, which would likely uphold it.
The change is about certainty: the seat is something the parties chose deliberately for the arbitration, so making its law the default for the arbitration agreement aligns the agreement with where the arbitration actually lives.
Draft it expressly either way
The practical response is simple and important: state the governing law of the arbitration agreement expressly. If you want the main-contract law to apply to it, you must now say so - the section 6A default will otherwise apply the seat's law.
Add a single line to the arbitration clause specifying that law. It removes the entire question, whichever way you decide, and avoids being caught out by the change in the default.
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Practical checklist
- Treat the arbitration agreement as separable, with its own governing law (s.7 Arbitration Act 1996).
- Know the default has flipped: Arbitration Act 2025 s.6A applies the seat's law unless you expressly agree otherwise.
- Do not assume the main-contract governing law covers the arbitration agreement - it is not an express choice (s.6A).
- For post-August-2025 agreements, expressly state the arbitration agreement's governing law.
- If you want the main-contract law to govern the arbitration agreement, say so explicitly.
- Check that the chosen law upholds the validity, scope, and formal requirements you need.
This guide is informational only and is not legal advice. It does not replace advice from licensed counsel on the facts of a specific transaction.
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