In the decades since World War II, we have constructed a system of regulatory law that basically outlaws common sense. Generally, landowners and developers welcome the exercise of judgment in the implementation of land use and development controls, provided the addition of this human ingredient improves the efficiency and predictability of the decision-making process and promotes pragmatic government flexibility that allows the developer to respond to the physical constraints of a site and changes in the market. But not quite. Realistically, the developer knows that review of a development project in light of today's more complex land use, growth and environmental considerations requires judgment to provide pragmatic resolution of these issues. It is when judgment is exercised arbitrarily that there is abuse of discretion.
Discretion is nothing more than the exercise of judgment.
In the context of land use and development approvals, discretion means substantive and procedural choices made by a legislative or administrative body such as a zoning commission. Generally speaking, when a decision-making body exercises judgment which exceeds the bounds of its delegated authority, then a case of abuse of discretion can be made. As originally conceived, zoning was supposed to require very little exercise of discretion. This premise was driven by a desire to avoid legislative or administrative interference with the land market. Zoning has not remained faithful to its original concept.