The law was passed with near-universal support, and was explicitly supported by the Conservatives when they won power in 2010. But then the Tories returned to type and decided to "get rid of all the green crap". In 2022 their Net Zero Strategy was ruled unlawful as it failed to quantify how it would meet the emissions budget. And now, the same has happened to its replacement:
The UK government’s climate action plan is unlawful, the high court has ruled, as there is not enough evidence that there are sufficient policies in place to reduce greenhouse gas emissions.An emissions reduction plan is not a PR document. Bullshit numbers and heroic assumptions of success may be normal in the world of business, but they're simply unacceptable in government.The energy secretary, Claire Coutinho, will now be expected to draw up a revised plan within 12 months. This must ensure that the UK achieves its legally binding carbon budgets and its pledge to cut emissions by more than two-thirds by 2030, both of which the government is off track to meet.
[...]
The judge agreed with ClientEarth and Friends of the Earth that the secretary of state was given “incomplete” information about the likelihood that proposed policies would achieve their intended emissions cuts. This breached section 13 of the Climate Change Act, which requires the secretary of state to adopt plans and proposals that they consider will enable upcoming carbon budgets to be delivered.
Sheldon also agreed with the environment groups that the central assumption that all the department’s policies would achieve 100% of their intended emissions cuts was wrong. The judge said the secretary of state had acted irrationally, and on the basis of an incorrect understanding of the facts.
(In the meantime the Tories have doubled down on denial, approving new oil and gas permits and rolling back measures to phase out dirty fossil fuel cars and heaters. So they're clearly unwilling to engage with their legal obligations).
The relevance to Aotearoa should be obvious: we borrowed the framework of our Zero Carbon Act direct from the UK. And like the UK, we currently have a government which professes commitment to its long-term net-zero target, while removing practically every concrete measure by which it might be achieved. That government is currently meant to be preparing its second Emissions Reduction Plan, which is legally required to meet the targets set by the second emissions budget, but its hard to see what it will have in it, other than some handwavium about renewable energy, "markets" and the ETS (which doesn't cover our largest polluters, and which National will then proceed to sabotage). Which means we can probably expect a similar court-case here. And if that happens, the UK precedents, while not binding, are likely to be very persuasive.