This study develops NusantaraLaw, a Domain-Adaptive Retrieval-Augmented Generation (RAG) system for Indonesian law via QLoRA fine-tuning of the Qwen 3.5 9B model on a national legal corpus. A dataset of 6,502 instruction-response pairs was curated from eight official legal sources and validated by two legal experts via Stratified Random Sampling (250 samples, margin of error 6.96 percent). Four…