Central to the implementation of the Act is Section 52 which requires Stormont departments to hit their own targets and cooperate to reach the overall net-zero goal.
In his judgement Mr Justice McAlinden ruled that the Department for Infrastructure was in breach of Section 52 as it had failed to produce the evidence to show that upgrading the A5 would be consistent with overall climate targets.
He found the department had instead made “aspirational assumptions”.
He said: “Section 52 does not prevent a major infrastructure project which is a source of significant greenhouse gas emissions being devised, promoted, constructed and put into operation.
“But what it does clearly rule out is the construction and operation of such a major project in the absence of robust planning, synchronisation and co-ordination between all NI government departments to ensure that the project fits into the plans, strategies and policies which map out a realistic and achievable pathway to achieving net zero by 2050.”