This chapter deals with conflicts and the legitimacy of environmental associations in conflict with, or holding to account, recent nickel projects in New Caledonia-Kanaky – Goro Nickel in the South and Koniambo in the North. Based on the concepts of environmental justice and resource conflicts, and on environmental management provisions, we discuss how environmental associations dealing with mining impacts raise their voice, gain legitimacy and intervene in environmental monitoring. The organisations CEK/Environord, ŒIL, CCCE and Rhéébù Nùù pursue different approaches and strategies. CEK was internal to the mining company KNS (Koniambo Nickel SAS) before becoming more “independent” under the label “Environord” (despite continuing financing from KNS). Rhéébù Nùù aimed to fight against the Goro Nickel project in the South before signing a pact with the Brazilian group Vale, with royalties and community benefits. ŒIL is advised by an independent scientific committee which gives it broader legitimacy. Its environmental monitoring allows it some participation in the project, but decision-making remains with the mining operators. Despite the important actions of these NGOs, the pro-independence party FLNKS and the upheavals in 2020 around the selling of the Goro Nickel smelter show that political authorities in New Caledonia-Kanaky are trying to obtain greater control over nickel extraction, processing and exportation themselves.