Many other nations assign independent bodies to oversee and mandate the delimitation of boundaries; however, in some nations the
legislature manages this process. In the United States, legislatures play a commanding role in the redistricting (as delimitation is referred to in the United States) of congressional districts. The redrawing of boundaries occurs after the
decennial census; single-member constituencies are responsible for the election of the legislators that govern this process. In 25 states the state legislature is responsible for creating the redistricting plan, but six states (Alaska, Delaware, North Dakota, South Dakota, Vermont and Wyoming) do not require redistricting for the House of Representatives and instead elect a single representative for the entire state. Each state has its own constitution and laws surrounding the redistricting process, and most of the modern criteria applied federally have come about through rulings by the U.S. Supreme Court. Prior to 1962, there was limited federal and state government regulation on redistricting, and these were rarely enforced. However, after the
Baker v. Carr (1962) decision redistricting became justiciable and courts became an active participant in the redistricting process of congressional districts as the decision allowed voters to challenge redistricting plans. Since
Shaw v. Reno (1993) and
Abrams v. Johnson (1997), the courts have invalidated numerous congressional redistricting plans upon the basis of traditional districting principles. These decisions have been surrounded in controversy as the Supreme Court has not identified these 'traditional' criteria explicitly, resulting in the major political parties attempting to abuse the lack of legislation and definition to advantage their respective parties. According to the database of redistricting laws in all fifty states and previous court decisions, the
de facto principles are: compactness, contiguity, equal population, and preserving county and city boundaries. == Extremes ==