By Nate Raymond
WASHINGTON (Reuters) -The U.S. Supreme Court on Monday turned away a Republican former congressman's challenge to a map charting Pennsylvania's U.S. House of Representatives districts that the state's highest court adopted in place of one drawn up by Republican lawmakers.
The justices declined to hear an appeal of a ruling by Pennsylvania's top court endorsing a map backed by a group of Democratic voters after Democratic Governor Tom Wolf vetoed a plan passed by the majority-Republican state legislature.
Pennsylvania has 17 House districts - down one after the state lost population in the most recent national census done in 2020.
The appeal of the February ruling was brought by former U.S. Representative Ryan Costello, who argued that the U.S. Constitution limits the ability of state courts to interfere with maps or rules adopted by state legislatures for federal elections.
Costello, who served in the House from 2015 to 2019, asked that the U.S. Supreme Court take up the case alongside a similar one out of North Carolina it agreed in June to hear to "rein in the state judiciaries' unconstitutional meddling in congressional redistricting decisions."
The North Carolina case, like the Pennsylvania one, involves a map drawn by a Republican-led legislature that a state high court rejected in favor of a different, judicially endorsed redistricting plan.
The Supreme Court in March declined to prevent the court-endorsed maps in both states from being used in primaries and the upcoming the Nov. 9 midterm elections, which will determine if Democrats retain control of the U.S. House.
But the Supreme Court, which has a 6-3 conservative majority, later in June agreed to hear the case out of North Carolina, which seeks to revive a map drawn by Republican state legislators.
In the Pennsylvania case, a group of Democratic voters had argued it was necessary for the judiciary to intervene and to draw new districts before the 2022 election cycle began after the legislature and governor had failed to reach a compromise on a map.
Costello's defense of the legislature's map relies on a contentious legal theory called the "independent state legislature doctrine" that is gaining traction in conservative legal circles and, if accepted, would vastly increase politicians' control over how elections are conducted.
Four of the U.S. Supreme Court's six conservative justices have previously expressed interest in having the court resolve whether state courts have authority to reject rules adopted by a state legislature for use in federal elections.
Costello also has argued that under a separate federal law, Pennsylvania should be now required to hold at-large elections until the state's congressional districts are redrawn in a manner he views as legal.
Lawyers for Wolf and the state's secretary of state in a brief had urged the justices to reject Costello's petition, saying he failed to raise his arguments at the state court level and lacked legal standing to pursue the case.
The dispute is one of numerous legal battles in the United States over the composition of electoral districts, which are redrawn each decade to reflect population changes measured in a national census. In most states, such redistricting is done by the party in power, which can lead to map manipulation for partisan gain.
(Reporting by Andrew Chung; Editing by Will Dunham)