This study examines the relationships between internal migration, climate change, and conflicts within communities residing near the most active volcano in East Java province, specifically Mount Semeru in Lumajang Regency. It examines the impact of climate change on natural disasters, such as volcanic eruptions. Since the issue of climate migration and displacement remains rare and under-studied by Indonesian and other scholars, this study offers a new perspective on migration, climate change, and conflict in Indonesia. Taking the case of villages relocation situated in the high-risk area of Mount Semeru eruption in Lumajang, this research aims at investigating the impact of climate change and natural disasters on the local communities that forced them to become the so-called ‘internally displaced persons’ (IDPs) in where the communities lost their life resources and sparked social conflicts between them. This study found that, as displaced persons, the villagers faced limited access to and rights to basic government services. These internally displaced people also continue to struggle to adjust to their new life in the relocation place and lose their access as a “normal” citizen, including their citizenship identification. This study finds that the livelihood insecurity, limited access to life support services, and prolonged social conflict experienced by internally displaced persons (IDPs) in Indonesia are significantly caused by incomplete and fragmented legal and regulatory frameworks governing post-disaster relocation. The absence of clear and detailed provisions concerning land and building ownership status in relocation areas, the issuance of temporary or new identity cards, and other administrative entitlements demonstrates substantive gaps in the existing disaster management regime. These issues are not explicitly and comprehensively regulated under Law Number 24 of 2007 concerning Disaster Management, Government Regulation Number 21 of 2008, nor Minister of Public Works and Housing Regulation Number 29/PRT/M/2018. As a result, implementation at the local level often lacks legal certainty and technical guidance, leaving IDPs in a vulnerable position. Based on these findings, this study recommends the formulation of more specific technical regulations on post-disaster relocation, particularly regarding land tenure security, civil registration, and inter-agency coordination. Further research is needed to examine the effectiveness of relocation policies in practice and to assess the long-term socio-economic impacts on displaced communities. © The Author(s), under exclusive licence to Springer Nature B.V. 2026.