A mix of established and emerging trends in domestic groundwater-related legislation is illustrated from a comparative law perspective. The analysis is arranged around a number of questions or issues the reader may wish to ask or explore, from who owns groundwater to what is regulated and how, from what role for groundwater users in resource governance to concern for the ecosystem-support function of groundwater, from the land/subsurface space/groundwater nexus to conjunctive use and managed aquifer recharge, to where groundwater regulation intersects the customary water practices of traditional communities. Also, the body of international law that governs relations between States as regards groundwater and aquifers that straddle international or interstate boundary lines is illustrated. Despite the scanty evidence on record, the implementation and enforcement of domestic groundwater legislation is briefly addressed, and the importance of such legislation to meet States’ obligations regarding transboundary groundwater and aquifers is emphasized. Advances in discrete segments of the groundwater regulatory spectrum, and strides in reaching out to non-groundwater regulation in view of its relevance to groundwater, are highlighted in conclusion, alongside advances in the codification of norms of States’ behaviour, and in the negotiation of treaties and agreements between States, regarding transboundary aquifers.