Case-to-Statute Retrieval—identifying applicable statutes from case facts—is essential for judicial efficiency but remains underexplored in low-resource languages like Vietnamese, where annotated legal corpora are scarce and domain-specific challenges persist. To advance research in this setting, we introduce ViCSR, a new benchmark of 10,000 Vietnamese criminal judgments and 1,122 statutory articles with citation-based relevance labels. We further propose a lightweight two-stage framework that performs efficient candidate retrieval with a fine-tuned Vietnamese bi-encoder and leverages citation structure for reranking with a compact heterogeneous GNN. Experiments show clear improvements over strong sparse and dense baselines, highlighting the importance of both domain adaptation and structure-aware modeling in low-resource legal IR. We will publicly release the benchmark, code, and checkpoints.