(1) the ECT integrates sustainable development as a core principle but needs to be updated since the EU/UK have greater commitments (now is effectively done)
(2) criticism towards investment arbitration is not about ECT, and it has not been subject to the modernisation process nor in the mandate of the Energy Charter Conference, it only addressed compatibility with EU law (now done by exempting the EU from intra-EU investment cases)
(3) like many, he confirms that w. 20 yrs sunset clause, withdrawal from the ECT makes little sense. Integrating Paris Agreement into ECT wouldn't create any difference since Paris Agreement doesn't have enforcement mechanisms (neither the ECT, it's all about national policies)
(4) on Vienna Convention (VCLT): a collective EU withdrawal from the ECT (an agreement on the ECT on the basis of VCLT) is challenging: as per VCLT art 41(1)(b)(i), the rights of other contracting parties can't be affected and the original Treaty objectives - can't be undermined
(5) he shares analysis of the legal expert community that the ECT remains a valid platform for new and renewable energies and that is better to have a modernised Treaty rather than the unreformed one.
Conclusion: amendments are generally good, withdrawal from the ECT makes little sense, Vienna Convention won't help in finding "back door" for an exit. Positive sides of the ECT has to be used instead (mainly investment protection which includes renewables).