The Constitution requires boundaries for U.S. House districts to be redrawn after each census. While that task typically is done by state legislatures, 13 states use commissions as part of their congressional redistricting process. The amount of legislative involvement with those commissions varies by state.

On Monday in a 5-4 ruling, the Supreme Court upheld Arizona congressional districts drawn by an independent commission. The decision preserves the efforts in Arizona and a dozen other states to limit partisan influence in redistricting.

Here's how redistricting works in those states, as categorized by the National Conference of State Legislatures.

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INDEPENDENT COMMISSIONS

ARIZONA — Congressional districts are drawn by a five-person commission established under a ballot measure approved by voters in 2000. It takes three votes to approve a map. Twenty-five potential redistricting commissioners are nominated by the same state panel that handles appeals court nominees. The Legislature's two Republican leaders choose two commissioners from 10 Republican candidates, and the two Democratic leaders chose two from their party's 10 nominees. Those four commissioners then select the fifth member, who must be an independent and serves as panel chairman.

CALIFORNIA — Congressional districts are drawn by a 14-person commission according to a 2010 voter-approved initiative. It takes nine votes to approve a map. A state auditor's panel takes applications and selects 60 potential redistricting commissioners — 20 Democrats, 20 Republicans and 20 others. The state Assembly and Senate majority and minority leaders each can eliminate two nominees from each political category. Eight redistricting commissioners are randomly selected from the remaining pool of candidates. Those commissioners then select the six other members of the panel.

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POLITICALLY APPOINTED COMMISSIONS

HAWAII — Congressional districts are drawn by a nine-person commission. The Senate president and House speaker each appoint two commissioners. The minority legislative party appoints two commissioners who, in turn, pick two more. The ninth commissioner is chosen by the other eight members of the panel.

IDAHO — Congressional districts are drawn by a six-member commission. Two-thirds of the commissioners must vote to approve a map. The majority and minority party leaders in each legislative chamber each select one person to serve on the commission; the state chairmen of the Republican and Democratic parties also each select a commissioner.

MONTANA — The state currently has only one congressional district. But if population growth triggers a second district, the Montana Constitution says the boundaries are to be drawn by the five-person commission that also draws state legislative districts. The majority and minority leaders of each legislative chamber appoint one member each. Those four then select a fifth member, who serves as chairman. The commission submits a plan to the Legislature, which can make recommendations, before the commission signs off on a final map.

NEW JERSEY — Congressional districts are drawn by a 13-member commission, which requires a majority vote to approve a map. If the commission cannot reach a majority, the state Supreme Court approves whichever of the commission's two leading proposals best conforms to U.S. law. The Senate president, Assembly speaker and minority leaders in each legislative chamber each appoint two commissioners. The state Democratic and Republican party chairmen each appoint two members. The final member is an independent chosen by the other members.

WASHINGTON — Congressional districts are drawn by a five-person commission, according to a plan that lawmakers sent to the ballot in 1983 and voters approved. At least three commissioners must vote to approve a map. Legislators can amend the plan with a two-thirds vote of each chamber, but their changes can shift no more than 2 percent of the population among districts. The majority and minority leaders in each legislative chamber appoint one commissioner each, who cannot be an officeholder or lobbyist. Those four members then select a fifth, nonvoting member who serves as chairman.

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BACKUP COMMISSIONS

CONNECTICUT — A bipartisan legislative committee is to develop a redistricting plan, which requires a two-thirds vote in each chamber for approval. If that fails, the task shifts to a nine-member commission, which can approve a map by majority vote. The majority and minority leaders of each legislative chamber designate two people each to serve on the commission. Those eight commissioners, who all were legislators during the most recent redistricting, then select a ninth member. If the commission fails to agree on a redistricting plan, the state Supreme Court can establish a redistricting plan.

INDIANA — If the legislature fails to pass a redistricting plan, a map is then drawn by a five-person commission. A majority vote of the panel is needed to send the plan to the governor, who then issues an executive order adopting it. The commission consists of the House speaker, Senate president pro tem and chairmen of the House and Senate committees responsible for legislative redistricting. The fifth member is a legislator, appointed by the governor.

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ADVISORY COMMISSIONS

IOWA — The nonpartisan Legislative Services Agency provides the legislature with a draft redistricting plan. If lawmakers reject it, the panel submits a new plan. If legislators reject the second version, a third plan is prepared. But unlike the first two, the third version can be amended by lawmakers before they vote on it.

MAINE — A 15-member commission drafts a congressional redistricting plan and submits it to the legislature, which can either enact it or approve its own plan by a two-thirds vote of each chamber. The House speaker and minority leader each appoint three members, and the Senate majority and minority leaders each appoint two. The chairmen of the state Democratic and Republican parties also serve as commissioners. Republicans and Democrats on the commission each select one additional member from the general public, and those two people then pick a third person from the general public.

NEW YORK — Under a constitutional amendment approved by voters last November, a 10-member commission will draft a proposed congressional district map following the next census. The legislature can approve or reject it. If lawmakers reject a second version, they can make changes to the plan before passing it. The majority and minority leaders of each chamber each appoint two members to the commission. Those eight members then select the other two commissioners.

OHIO — A six-member task force provides help to the legislature in developing a congressional redistricting plan. The task force consists of three people each appointed by the House speaker and Senate president. At least one appointee from each leader must be someone who is not a lawmaker.