There are many drivers of the epoch-defining environmental crisis that the biosphere - and humankind as part of it - faces today, as we embark on the critical 2020-2030 decade. The main one, by many accounts, is the reliance by one species, humans, on a certain form of energy, derived from fossil fuels, as the backbone of their modern conception of 'civilisation'. Burning fossil fuels is not only at the roots of the environmental crisis, but at the foundations of how humans produce shelter, heat, food, transportation and most of their cultural products, including technology. From the narrow lenses of the social practice we call international law, energy may appear as a sub-topic, alongside so many others. In reality, international law is but one aspect of a wider order shaped, since the dawn of the so-called 'Industrial Revolution' in the late XVIII Century, by fossil fuel energy. Rather than a mere 'branch' of the narrow social practice of international law, it is international law which is an aspect of an energy order, a historical socio-technical regime. This socio-technical regime is, however, not like its predecessors. The fossil fuel-based order has come to encompass, by its Earth-shaping effects, the entire biosphere, including humanity. And we now understand that it challenges a much more profound layer of 'regulation', a resilient but threatened biospheric balance that was, for centuries, taken for granted