The European Union
(EU) and its Member States have taken steps to eliminate intra-EU investment
arbitration and the applicability of the sunset clause in intra-EU relations
under the Energy Charter Treaty (ECT) through a declaration and a treaty.
However, it is uncertain whether either the declaration or the treaty will have
the intended effect. The declaration cannot be qualified as an authentic
interpretation under Article 31(3)(a) Vienna Convention on the Law of Treaties
(VCLT), although it is of a different nature than the 2019 Achmea declarations.
It could potentially qualify as an inter se agreement under Article 41 VCLT.
The envisaged treaty certainly constitutes an inter se agreement. However, it
is doubtful whether either the declaration or the inter se treaty meet the
substantive requirements of Article 41(1) VCLT. Although neither Article 16 ECT
nor Article 46 ECT explicitly prohibit inter se agreements, arbitral tribunals
may find that the removal of intra-EU arbitration and the sunset clause are incompatible
with the effective execution of the object and purpose of the ECT as a whole
under Article 41(1)(b)(ii) VCLT. However, the inter se removal of Articles 2,
16 and 46 ECT would mitigate this argument. In addition, the notification
requirement of Article 41(2) VCLT must be respected.