‘Reasonable use of the waters of rivers’ in a changing climate – a potential constitutional challenge to Australian Commonwealth approvals of export-oriented fossil fuel extraction

Several climate-based court challenges to Australian Commonwealth government actions, particularly fossil fuel development approvals, have failed. This was in part because they lacked a strong statutory basis and hence the courts declined to find new ‘implied’ duties or responsibilities of the Commonwealth and its Ministers. This article proposes that the largely overlooked Section 100 of the Australian Constitution could form the statutory basis of a challenge to Commonwealth government environmental approvals of export-­oriented fossil fuel extraction projects. Section 100 protects Australian State residents’ ‘right … to the reasonable use of the waters of rivers’ from abridgement by Commonwealth laws governing ‘trade or commerce’, made under Section 51(i) of the Constitution. Section 100 may prevent the Commonwealth from approving export-oriented fossil fuel extraction under the Environment Protection and Biodiversity Conservation Act 1999 (Cth) or the Foreign Acquisitions and Takeovers Act 1975 (Cth) because the High Court of Australia has previously held that these laws rely upon Section 51(i) for their constitutionality, and because the climate warming effects of exported fossil fuels’ Scope 3 emissions and the consequential drying effects on Australia’s rivers would abridge the ‘reasonable use’ of their waters. It is argued that, by virtue of its grounding in the Constitution, this case would overcome many of the Commonwealth’s previous arguments in climate-based cases, including that courts should not set government policy; that Australia’s contributions to global warming are small and subject to market substitution; that exported (Scope 3) emissions are not Australia’s responsibility; and that the harm caused by future climate change is too indeterminate for courts to rule upon. Some implications for future Commonwealth policy are considered.