ScottishPower: suspensive conditions and regulatory uncertainty

ScottishPower Renewables (UK) Ltd v Scottish Ministers [2026] CSOH 86 concerned whether Scottish Ministers lawfully refused consent for the Carrick Forest wind farm despite a proposed suspensive condition intended to deal with unresolved aviation-lighting mitigation.

The Outer House rejected the judicial review. The judgment is useful beyond wind energy because it deals with how far a decision-maker must investigate changing information, what counts as a mandatory relevant consideration, how reasons are read and where judicial review stops short of re-making a planning or regulatory judgment.

Neutral citation

[2026] CSOH 86

Court

Outer House, Court of Session

Judgment date

10th September 2026

Judge

Lord Harrower

Case number

P142/26

Carrick Forest and the aviation-lighting problem

ScottishPower applied in December 2021 for consent under section 36 of the Electricity Act 1989, together with deemed planning permission under section 57(2) of the Town and Country Planning (Scotland) Act 1997, for a wind farm at Carrick Forest near the Galloway Dark Sky Park. The amended scheme included 12 turbines up to 200 metres high.

Turbines of that height engage aviation-lighting requirements. ScottishPower proposed an Aircraft Detection and Obstacle Lighting System, or ADLS, so that warning lights would illuminate when relevant aircraft approached rather than remaining continuously lit through the night.

That mitigation depended on a wider regulatory process. In particular, ScottishPower would need an airspace change proposal approved by the Civil Aviation Authority for a transponder mandatory zone around the wind farm. There was uncertainty about the technical trials, the applicable CAA guidance, the timing of regulatory approval and whether the airspace change would ultimately be approved.

The proposed suspensive condition

ScottishPower proposed a condition preventing development from commencing until an aviation-lighting mitigation plan, including ADLS, had been approved by the Scottish Ministers after consultation with the CAA and Ministry of Defence.

The public inquiry was conjoined with inquiries into the neighbouring Craiginmoddie and Knockcronal wind farms. Reporters recommended approval of those two schemes but refusal of Carrick Forest. A critical concern was whether ADLS could actually be approved and delivered within a reasonable period.

The reporters nevertheless made clear that, if Ministers disagreed with that assessment and considered ADLS deliverable within a reasonable timescale, Carrick Forest could be approved subject to the proposed suspensive condition.

Why Ministers did not use the condition

Scottish Ministers eventually refused the application. They considered a suspensive condition but concluded that the evidence did not give sufficient assurance that the proposed ADLS mitigation could be delivered within the usual five-year implementation period.

ScottishPower said the condition was the proper answer to the remaining uncertainty. It also argued that the decision had been taken more than a year after the inquiry report, during which time the technical and regulatory position had moved on.

Those arguments produced four grounds of judicial review: an alleged failure to make sufficient inquiry, failure to take account of relevant considerations, irrationality in the treatment of the five-year period and inadequate reasons.

Post-inquiry information does not disappear

Lord Harrower rejected the proposition that considering new information after an inquiry would distort the statutory process. Where time has passed, a decision-maker may have to consider whether new information or changed circumstances could materially affect the decision.

If genuinely new evidence leads Ministers to contemplate departing from reporters’ recommendations, procedural fairness may require the applicant, planning authority and other inquiry parties to be given an opportunity to respond.

But that does not mean every later document or update must be passed unfiltered to the ultimate decision-maker. Officials are entitled to assess what is genuinely new and whether it is likely to be material.

On the facts, the court found no material change in the fundamental uncertainties identified by the reporters. The Mark Hill trials remained incomplete, the relevant CAA guidance had not yet been finalised when the decision was made, and approval of the required airspace change remained uncertain.

Relevant does not always mean mandatory

The judgment applies the public-law distinction between a consideration that may be relevant and one that the decision-maker is legally obliged to take into account.

Outside matters expressly or impliedly required by statute, an omitted consideration must be so obviously material that it would be irrational not to consider it. A decision-maker is not legally required to work through every matter that could conceivably be relevant.

ScottishPower did not show that the later ADLS material crossed that threshold. The court also rejected the argument that Ministers had unlawfully overlooked the commercial reality that a developer might not take forward the costly regulatory work without first having consent. Ministers had plainly made similar judgments in other wind-farm cases. Whether that approach was too conservative was a matter of judgment, not a basis for the court to substitute its own view.

The court would not turn judicial review into a planning rehearing

The parties produced competing affidavit evidence about how the CAA airspace-change process might work and how quickly the necessary approvals might be obtained.

The court declined to resolve those factual disagreements as though it were the original consenting authority. Doing so would risk dragging judicial review into the merits of the Scottish Ministers’ decision.

That is an important practical limit. Judicial review asks whether the public decision was lawful. It does not give the court a general licence to decide whether a regulator, planning authority or Minister was commercially or technically over-cautious.

The five-year wording was untidy, but not unlawful

ScottishPower criticised the decision letter because it referred variously to ADLS or the development being installed, deployed or implemented within five years. The proposed condition itself required approval of the mitigation before commencement, not completion of the whole ADLS installation before construction began.

Lord Harrower accepted that the decision was not happily worded. Read fairly and in context, however, the five-year references were to the period within which development had to commence. The court considered it inherently unlikely that Ministers had misunderstood the agreed commencement conditions as requiring the whole development to be completed within five years.

The reasons challenge also failed

The court applied the familiar rule that reasons must be intelligible and adequate and must enable the reader to understand why the principal controversial issues were decided as they were. They do not need to address every material consideration.

Here, the regulatory and technical uncertainties had already been examined in the inquiry report. Ministers agreed with the reporters on those matters. The informed reader was therefore not left in real or substantial doubt about why consent was refused.

Why the case matters beyond Scottish wind farms

This is a Scottish Court of Session decision. Its statutory setting is section 36 of the Electricity Act 1989 and deemed planning permission under the Town and Country Planning (Scotland) Act 1997. It should not be presented as if English planning legislation applied directly.

There are, however, wider public-law lessons. The judgment draws on UK authorities on the duty of inquiry, relevant considerations and reasons. Those principles can matter wherever a planning or consenting decision depends on an unresolved external approval, later evidence or a proposed condition intended to defer detailed resolution.

Practitioners in England may recognise the practical issue as similar to a Grampian-style condition: can permission sensibly be granted now where an essential step depends on a third party or separate regulatory process? ScottishPower shows that proposing a suspensive condition does not compel a decision-maker to accept the regulatory or delivery risk it leaves behind.

The further lesson is evidential. If the case for a condition depends on a future approval being realistically obtainable within the development programme, the evidence should address the regulatory pathway, timing, remaining technical uncertainty and the consequences if approval is delayed or refused.

Source

This page has been prepared from the complete 32-page judgment published by the Scottish Courts and Tribunals Service. The judgment PDF is available below for Gold members.

View the official Scottish Courts judgment.

ScottishPower Case Law Page Published: 15th September 2026