Many states specifically require some sort of judicial or administrative agency review of deannexation petitions.
When they occur, they are typically small-scale and involve individual properties; deannexations of entire neighborhoods are unusual.
For example, cities sometimes deannex land in order to rationalize strange borders created by past annexation wars.
[8] A great deal of deannexation research has focused specifically on the San Fernando Valley dispute.
[8] Majority-white cities have sometimes attempted to deannex regions with large minority populations in order to preserve white voters' power.
Some grassroots deannexation campaigns have likewise been initiated by majority-white areas, motivated by what Richard G. Hatcher described as "white reaction to black ascendency".
[13] From the standpoint of separation of powers, deannexation is a legislative function because it relates to municipal boundaries, which are traditionally reserved to the legislature.
[14] However, a few cases have held that courts have a equitable power to deannex land to which no municipal services are provided.
[20] Eleven of the 28 states allowed petitions only when the deannexation would not create a "donut hole" inside an existing municipality.
For example, for homeowners otherwise inclined to leave a city, deannexation provides the benefits of avoiding the expense of relocation and increased commuting times.