Delimitation refers to the process of demarcation of the boundaries of parliamentary or assembly constituencies. The process is carried out every few years to ensure that each constituency has approximately an equal number of voters — the underlying logic being that a set number of voters have one representative in the Lok Sabha as well as in the state assemblies across the country. Therefore, the exercise is carried out after every census.
Given the political sensitivity of the exercise, no government — central or state — can carry it out, and after every census, Parliament enacts a Delimitation Act under Article 82 of the Constitution. Subsequently, a high-powered body known as the Delimitation Commission is constituted, which carries out the process of demarcation of constituency boundaries. The orders of this commission are legally binding and not subject to scrutiny of any court of law. Even Parliament cannot suggest modifications to an order issued by the commission.
The commission consists of a chairman — a retired or sitting judge of the Supreme Court — the chief election commissioner or any of the two election commissioners, and the election commissioner of the state in which the exercise is being carried out. In addition, five MPs and five MLAs of the state are chosen as associate members of the commission.
Since the commission is a temporary body with no full-fledged staff of its own, it relies on EC employees to carry out the long-drawn exercise. Census data for each district, tehsil and gram panchayat is collected, and the new boundaries are demarcated. The exercise can take up to five years.