Last week, the Federal Court found that the Commonwealth minister for the environment owed a duty of care to eight Australian children when exercising her statutory functions to approve or not approve a coal mine under the Environment Protection and Biodiversity Conservation Act 1999 (Cth). The implications of this decision are extremely significant, but it is also likely to be the first step in a long journey.

To understand what the decision means, it is helpful to appreciate that this new duty of care operates in the same way as long-established duties of care: for example, a doctor’s duty of care to a patient, a manufacturer’s duty of care to a user of its goods, or a lawyer’s duty of care to a client. The first such duty of care was imposed by the House of Lords in 1932. Famously, it was a duty of care imposed on a ginger beer company towards its customers and, in particular, a Mrs Donoghue, whose drink was alleged to have contained a snail.

The principle established by that case, known as the ‘neighbour principle’, is that a person must take reasonable steps not to cause foreseeable harm such as might occur to one neighbour. It is probably not a coincidence that the principle emerged in its current form at a time when the Great Depression had wreaked havoc on the world and capitalism was undergoing a rare period of abeyance. In 2001, the NSW Chief Justice described it as ‘the last outpost of the welfare state’ and went on to say: ‘there have been changes over recent decades in the expectations within Australian society about persons accepting responsibility for their own actions.’

However, the rise of neoliberal individualism has not robbed the neighbour principle of its teeth. Since the snail case, it has been progressively expanded to apply to new categories of relationship. In that sense, what the Federal Court has done in this latest decision is an entirely orthodox application of long-established principles. It is the effect of the decision, not the reasoning behind it, that is potentially revolutionary.

A number of things about the judgment are remarkable, however.

There was unchallenged expert evidence about the consequences of global warming of 4 degrees above pre-industrial levels. This was nothing short of apocalyptic. In Australia, much of the mainland would become uninhabitable for humans except for ‘artificial enclosed environments’. Brisbane, Sydney, Melbourne, Adelaide and Perth would ‘suffer increasing inundation and flooding from storm surges as sea level rises to metres above its pre-industrial level over the coming centuries’. The Great Barrier Reef would cease to exist.

The risk of harm to the children who brought this case is to be measured against this extreme scenario. Importantly – and whilst this new doctrine does not demand that the minister do whatever is possible to protect against the threat – the gravity of the potential harm informs what steps will be considered ‘reasonable’ to prevent it.

It is also notable that the Court did not accept the minister’s argument that the duty of care was inconsistent with the statutory duties conferred on her by the Act. Whether or not the existence of the duty is ‘coherent’ with the Act is likely to be a point on appeal. It is also a way in which the government may seek to rob this development of its effectiveness as a tool for combating climate change: it is open to the legislature to explicitly state that the duty of care does not exist, provided, of course, it has the votes to do so. One can imagine the hand-wringing already taking place inside the Labor party.

Before it gets to that point there will almost certainly be an appeal, and likely a second appeal to the High Court, meaning that the status of this new duty is not likely to be locked down for twelve to eighteen months at the earliest. But until the issue is settled, there will be an ongoing question about whether politicians have a duty to consider climate change risks when making decisions under current statutes. And even more vexing for politicians will be the risk that they if do not do so, or do not do so properly, their decisions will be rendered invalid.

In last week’s case, the Court did not determine that point. Justice Bromberg declined to pre-emptively order that a decision to approve the coal mine would be invalid. This was because the applicants had not satisfied him that ‘a more nuanced response from the Minister, something short of unconditional approval, is necessarily unavailable as a reasonable response to the foreseeable harm to the Children’. In other words, the duty of care does not necessarily lead to the demand that there be no more coal mines, but a carte blanche approach is out. Nor did Justice Bromberg decide that a negligent exercise of the minister’s statutory power would necessarily be invalid. He expressed ‘reservations’ about whether that was correct, an issue that can only be adjudicated upon if and when this or another mine is actually approved. If approvals can be set aside because the statutory power to approve them was exercised negligently, the scope of the duty of care would be enormous, potentially invalidating approvals for everything from coal mines to housing developments (although the question of whether the new duty is coherent with the relevant Acts in each state is a matter to be thrashed out in other courts).

The mere prospect that such approvals might be declared invalid because they fail to take climate change risks into account is one that will keep many developers, coal barons and politicians awake at night.