“… Lord Carnwath said special duties arose under the EIA Regulations where an application (as in this case) involved a development which was “likely to have significant effects on the environment by virtue of factors such as its nature, size or location” (an “EIA development”).
Regulation 3(4) provides that decision-makers shall not grant planning permission, where the application involves an EIA development, without first taking the environmental information into consideration, and that they must state in their decision that they have done so.
The judge also noted that article 6.9 of the Aarhus Convention (Convention on Access to Information, Public Participation in Decision-making and Access to Justice in Environmental Matters), to which the United Kingdom is a party, also required each party to make accessible to the public the text of certain decisions involving an EIA, along with reasons and the considerations on which it is based.
Lord Carnwath said that “where there is a legal requirement to give reasons, what is needed is an adequate explanation of the ultimate decision”.
He added: “The content of that duty should not in principle turn on differences in the procedures by which the decision is arrived at. Local planning authorities are under an unqualified statutory duty to give reasons for refusing permission. There is no reason in principle why the duty to give reasons for grant of permission should become any more onerous.”
The essence of the duty, and the central issue for the court, was whether the information so provided by the authority leaves room for genuine doubt as to what it has decided and why.
The Supreme Court rejected Dover’s argument that a breach of the EIA duty alone should be remedied by a mere declaration of the breach.
Dover had sought to rely on R (Richardson) v North Yorkshire County Council  1 WLR 1920 in which the Court of Appeal remedied a failure to provide a statement of reasons without quashing the decision, by ordering only that the statement be provided.
However, Lord Carnwath said in that case it was possible to take the planning committee as adopting the reasoning in the officer’s report which had recommended granting permission.
The Supreme Court judge said that in view of the specific duty to give reasons under the EIA regulations, it was strictly unnecessary to decide what common law duty there may be on a local planning authority to give reasons for grant of a planning permission. “However, since it has been a matter of some controversy in planning circles, and since we have heard full argument, it is right that we should consider it.”
Lord Carnwath said the particular circumstances of the Dover case would, if necessary, have justified the imposition of a common law duty to provide reasons for the grant of permission.”