In the United Kingdom, the final proposals of the four Boundary Commissions take effect only after an affirmative vote by Parliament. But Parliament's power to accept or reject a plan is a formality. The only two exceptions were in 1948, when Parliament proposed the addition of seventeen seats for under-represented urban areas, and in 1969, when Parliament delayed the implementation of a redistribution plan on the grounds that impending changes to local government boundaries would render the plan obsolete. Conservatives viewed both of these actions by the Labour government as political. The United States is the anomaly with regard to legislatures and the adoption of redistricting plans.
Most states assign the task of federal redistricting to the state legislature.
The few that assign the task to an agency or a commission still require an affirmative vote of the state legislature to enact a redistricting plan. In fact, many plans adopted by legislatures do favour one political party over others. Still, plans drawn by neutral commissions can also produce politically biased election outcomes, however unintentional.