Protest group Together Against Sizewell C launched a bid to challenge development consent granted for the multi-billion-pound project in Suffolk by then business secretary Kwasi Kwarteng in July 2022.
At a hearing in March this year, lawyers for the group of local residents argued the government failed to assess possible environmental impacts, including that of providing an "essential" water supply to the project.
They also said the government did not consider "alternative solutions" to meeting its energy and climate change objectives.
The government, ostensibly supporting the project with a £700m stake, argued it made "legitimate planning judgments" and that the campaigners' bid was "unarguable".
In a 47-page ruling on Thursday (22 June), Mr Justice Holgate dismissed the opposition group's legal challenge, adding that several parts of it were "totally without merit".
The judge said there was "nothing artificial or unlawfully limiting" about a policy aimed at providing a mix of solar, wind and nuclear power.
He added: "The claimant's argument depends upon an illegitimate attempt to rewrite the government's policy aims by pretending that the central policy objective is at a higher level of abstraction, namely to produce clean energy, without any regard to diversity of energy sources and security of supply.
"But it is not the role of a claimant, or of the court, to rewrite government policy, or to airbrush objectives of that policy which are plainly of 'central' or 'core' or 'essential' importance."
Mr Justice Holgate also found that the government's approach to the water supply, which would be dealt with under a separate process, was lawful.
French energy giant EDF, due to develop the project, previously said Sizewell C is expected to generate low-carbon electricity to supply six million homes.
Ministers have previously said the project could create 10,000 highly skilled jobs, with its eventual go-ahead being welcomed by unions and the nuclear industry.
During the two-day hearing in London, lawyers for the campaigners also argued that the government irrationally concluded the power station site would be clear of nuclear material by 2140, when rising sea levels and storm surges could flood the site before it has been decontaminated.
However, Mr Justice Holgate said: "It is obvious that the issue of how far into the next century spent fuel will need to remain at Sizewell C is subject to uncertainty. On any fair reading of the panel's report and the decision letter, that uncertainty was recognised."
Following the unsuccessful challenge, Together Against Sizewell C was ordered to pay £10,000 towards the Department for Energy Security and Net Zero's legal costs.
The Sizewell C megaproject has proved divisive and its gestation continues to be somewhat protracted.
In July 2022, the UK government gave the green light to the nuclear power station project, to be situated on the Suffolk coast adjacent to the Sizewell B nuclear plant, itself due to be decommissioned in 2035 although it may continue operating until 2055, if granted approval by the regulator.
One month later, then-Prime Minister Boris Johnson approved government funding for the Sizewell C nuclear plant, in one of his final acts as his time in office dwindled, although this decision was contentious with Treasury staff. At that time, the UK government was committing itself, at least in theory, to buying a 20 per cent stake in the plant for £6bn and to seek private funding to finance the remaining cost of the project, estimated to be £20-30bn.
On 1 September, Johnson promised £700m in government funding for the Sizewell C project, although by early November Sizewell C had been placed under review, as the new UK government's plan was to limit its spending overall. This included a formal review of the Sizewell C project.
Researchers have identified the typical problems that beset megaprojects and ultimately cause many of them to fail. E&T has looked into the often tortuous shepherding of megaprojects to completion in greater detail in a special feature.
