My understanding of Achmea is that the Court considers it contrary to EU law for a MS to enter into an agreement which may cause it to be bound by decisions of a tribunal if (i) the tribunal may take decisions affecting EU law in that state — which is almost inevitable for any trade or investment tribunal, and (ii) it can not refer questions to the Court, and (iii) there is no possibility to substantively review the decisions in the MS courts. (europeanlawblog.eu)
We also represent clients in judicial review applications arising from decisions of those tribunals and administrative bodies as well as complaints brought before the Ombudsman. (guildyule.com)
The reasonable apprehension of bias could not be validated by the later decision of the tribunal. (ngariss.com)