Through a study of the U.S. Army Corps of Engineers' (USACE) environmental assessment (EA) of the Dakota Access Pipeline's crossing of Lake Oahe near the Standing Rock Sioux Reservation, this paper explores regulatory agencies’ “interpretive implementation.” We find that, in implementing the National Environmental Policy Act and Executive Order 12898 on Environmental Justice, USACE “scope-shifted”—facultatively expanding and contracting the scopes of its spatial, scientific and cost–benefit impact analyses—to expedite industrial expansion, contravening the policies’ original intents. In doing so, USACE's EA created various energy injustices by excluding local tribes (especially the Standing Rock Sioux and Cheyenne River Sioux Tribes) and their concerns, e.g. treaty rights, local histories, climate change and especially potential oil spills with impacts on human health and subsistence resources. We analyze this scope-shifting through the lens of Karl Polayni's double movement between socioenvironmental protections and capitalist development. We elaborate this framework further via a triple-helix model that analyses ideologies, power relations and policies (here further complicated by both “law” and “interpretation” threads), as three intertwined strands that pull with or against each other, jointly progressing toward greater rights for vulnerable communities, “retrograding” toward earlier, oppressive conditions or simply stagnating. Ultimately, we argue that understanding scope-shifting and other forms of interpretive implementation as threads within the triple-helix policy strand, in dynamic tension or synchrony with other threads and strands, can help explicate agency decision-making processes. We hope that this conceptualization can elucidate the capacity of seemingly mundane bureaucratic practices for exacerbating, or potentially alleviating, energy injustice.