In several basins, groundwater is being withdrawn faster than it recharges, and some aquifers took thousands of years to fill. Unlike surface water, the loss is effectively permanent on any human timescale, and land subsidence from over-pumping cannot be reversed. Supporters of regulation argue this is the clearest case for intervention. Opponents respond that groundwater has historically been governed by state and local rules tied to land ownership, and that changing that is a property question.