This study examines how the Ultimum Remedium principle is operationalised in Indonesian mining law enforcement, particularly with respect to administrative sanctions, compliance with the mining Work Plan and Budget (Rencana Kerja dan Anggaran Biaya, RKAB), environmental restoration, and criminal enforcement thresholds. Although the principle is widely recognised as requiring the use of criminal law as a last resort, its practical application in the mining sector remains unclear. This study adopts a socio-legal research design combining semi-structured interviews, questionnaire data, regulatory review, and comparative legal analysis. The empirical data consist of interviews with 24 informants and questionnaire responses from 68 respondents representing government officials, mining company representatives, civil society organisations, and affected communities. The comparative analysis examines selected materials on mining and environmental enforcement from Australia, Canada, Chile, and Indonesia. The findings show that stakeholders generally accept the Ultimum Remedium principle, but they attach different operational meanings to it. Government officials frame it as a proportional enforcement procedure, mining companies associate it with legal certainty, civil society organisations emphasise accountability, and affected communities evaluate it through environmental restoration outcomes. The PT GMS case further illustrates weak sequencing between RKAB-related non-compliance, administrative correction, restoration obligations, and possible criminal escalation. Comparative legal findings indicate that Australia, Canada, and Chile situate punitive enforcement within broader systems of compliance supervision, administrative correction, restoration, and documented escalation mechanisms. The study implies that Indonesian mining enforcement requires a staged but flexible model that distinguishes correctable administrative non-compliance from serious, repeated, fraudulent, corrupt, obstructive, or environmentally harmful conduct. The originality of this study lies in its integration of stakeholder perceptions, RKAB compliance, an illustrative mining case, and comparative enforcement models to operationalise Ultimum Remedium as an institutional sequencing framework rather than merely a criminal law doctrine.