Every decade, American legislative districts are redrawn to reflect population change. Who draws them and what constraints apply differ by state, and both facts drive the litigation that follows.
Reapportionment comes before redistricting
The census first determines how many House seats each state receives, a calculation performed by formula from the national population count.
States gaining or losing seats must redraw everything, while states with unchanged totals still adjust boundaries because population shifted internally.
Districts within a state must be close to equal in population for congressional seats, a requirement derived from constitutional decisions and applied strictly.
Who holds the pen varies
In most states the legislature draws the maps, passing them as ordinary legislation subject to the governor's signature or veto.
Several states assign the task to independent or bipartisan commissions, created by ballot measure or statute, with rules limiting who may serve.
Others use backup commissions that act only when the legislature deadlocks, and a few have courts draw maps when the process fails entirely.
Criteria conflict with one another
Common requirements include contiguity, compactness, respect for county and municipal boundaries, and preservation of communities of interest.
These frequently point in opposite directions. A compact district may split a city, and following county lines may produce an irregular shape.
Ranking the criteria is therefore a policy decision, and states that specify an order of priority generate fewer disputes than those that list them without hierarchy.
Two kinds of challenge follow
Claims under federal voting rights law argue that a map dilutes the voting strength of a protected group, and these are litigated in federal court.
Claims of partisan advantage have largely moved to state courts, following a federal decision that such questions are not resolvable under federal constitutional standards.
State constitutions vary in whether they contain fairness provisions, so the same map pattern may be actionable in one state and not in another.
Timing shapes the outcome
Courts are reluctant to change maps close to an election, on the reasoning that late changes confuse administration and voters.
Litigation that runs long can therefore leave a disputed map in use for one or more cycles before a ruling takes effect.
The practical consequence is that the calendar influences results as much as the legal merits, which is why filing deadlines are contested alongside the maps themselves.