Defence — Exclusions and reservations — Energy Charter Treaty, Article 21 — Taxation measures — Interpretation — Municipal law — Whether the carve-out depended on municipal tax law — Whether the solar levy was paid for a specific purpose of reducing the incentive regime or for general State revenue — Whether the solar levy was a tax in nature and substance — Whether the solar levy had been characterised as a tax by the municipal courts — Whether the measure was rendered as a tax to avoid international arbitration proceedings

Fair and equitable treatment — Full protection and security — Arbitrary or unreasonable measures — Legitimate expectation — Legal stability — Whether the standards of protection were overlapping — Whether guarantees of stability in general legislation may ground a legitimate expectation that the regulatory framework would not be modified

Fair and equitable treatment — Legitimate expectation — Legal stability — Defence — Margin of appreciation — Due diligence — Whether investor awareness of possible changes to the legal framework may amount to a defence — Whether the claimants should have been aware of political and economic unrest and therefore impending reform — Whether the State should be accorded a margin of appreciation to make changes to the legal framework

Fair and equitable treatment — Legitimate expectation — Legal stability — Municipal law — Retroactivity — Whether expectations of stability may arise in the absence of an express stabilisation commitment — Whether there was a free-standing obligation to provide a stable and predictable investment framework — Whether State officials had made a promise of stability — Whether the State was entitled to amend legislation to correct price distortion — Whether a five-year tax exemption was a guarantee that the legal framework would not be amended during that period — Whether the measures were retroactive or in breach of legitimate expectations according to the municipal courts

Arbitrary or discriminatory measures — Windfall profits — Consumer welfare — Whether the solar levy was advanced as part of a rational package of measures to limit consumer prices and to raise revenue — Whether it was reasonable to regulate windfall profits