Scottishministers and energy firm SSE are challenging a judicial review decision that blocked plans for a 67-turbine wind farm near Loch Ness.
A judge at the Court of Session said in December that the Scottish government's decision to approve the wind farm near Fort Augustus was "defective".
Following a judicial review, Lord Jones said ministers reached their decision on SSE's Stronelairg project "in breach of environmental obligations".
Landscape charity the John Muir Trust sought the review after the wind farm was given planning consent last year.
The trust said the turbines would "destroy the character" of wild land.
Judges at the Court of Session in Edinburgh are this week due to hear an appeal against the judicial review which overturned the decision to give the go-ahead to a giant wind farm in the heart of the Monadhliath Mountains.
Energy Minister Fergus Ewing granted permission for SSE Renewables' project in July, 2014.
It was said at that time the wind farm could generate enough electricity to power 114,000 homes.
The operators also said it would bring £30m-worth of benefits to the region.
But in December 2015, that decision was overturned in the Outer House of the Court of Session by the late Lord Jones in a judicial review by Scottish conservation charity John Muir Trust.
The project is now to go before the Inner House of the Court of Session after the Scottish Ministers and SSE lodged an appeal. The hearing is expected to last three days between Wednesday, May 4 and Friday, May 6.
The court had previously heard that Scottish Natural Heritage had objected in principle to the wind farm's proposed site.
Lord Jones said: "If the ministers did take into consideration SNH's objection in principle to any wind farm development at Stronelairg, they have given no reason for rejecting it, and the decision is defective on that account."
The public was also denied an opportunity to comment on a revised planning application for the proposed wind farm, the judge said.
John Muir Trust argued the development would "destroy the character" of an area of wild land in the Monadhliath Mountains.
Stuart Brooks chief executive for the John Muir Trust said: “We are disappointed that this application has come back to court, and we don’t believe it’s a sensible use of public money. We would have preferred that the developer SSE had been asked to resubmit the application and then follow due process.”
The decision by Scottish Ministers to allow the project to go ahead was taken despite the Scottish Government’s own advisors Scottish Natural Heritage advising that a wind farm should not be built at Stronelairg because of its wild land qualities."
SSE had originally sought permission for up to 83 turbines at Stronelairg near its Glendoe hydro electric scheme above Fort Augustus.
However, in April 2013, Highland councillors voted 11 to three in favour of raising no objection on the understanding the project was reduced to 67 turbines.