MARY LOUISE KELLY, HOST:

The U.S. Supreme Court heard arguments today in the marquee case of the term, a case that could radically reshape the way federal elections are conducted across the country. NPR legal affairs correspondent Nina Totenberg reports.

NINA TOTENBERG, BYLINE: At issue is the so-called independent state legislature theory, put forth in this case by the North Carolina Republican State Legislature. If adopted, it would give state legislatures the power to put in place all manner of election laws and rules without any review by the state courts. At its most extreme, the theory could eliminate not just state judicial power over elections, but governor's vetoes. And it might allow state legislatures to certify presidential electors who were not approved by the voters - an idea that Donald Trump tried unsuccessfully to put forth in 2020.

In the particular case before the justices, the North Carolina Supreme Court ruled that the Republican-dominated state Legislature, in drawing new congressional districts after the 2020 census, violated the state constitution with an extreme partisan gerrymander. During almost 3 hours of arguments, three camps of justices emerged today. The court's three most conservative justices - Thomas, Alito and Gorsuch - favored some version of the independent state legislature theory. The three most liberal justices - Sotomayor, Kagan and Jackson - did not. And somewhere in between were Chief Justice Roberts and Justices Kavanaugh and Barrett.

First up was lawyer David Thompson, representing the Republican state Legislature. He told the court that the state courts have no authority under the U.S. Constitution to rule on congressional redistricting maps. Justice Jackson reacted with incredulity.

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KETANJI BROWN JACKSON: Is your argument that the state constitution has no role to play - period?

DAVID THOMPSON: That is our position.

TOTENBERG: Thompson subsequently qualified that answer, contending that the state courts could review procedural issues but not substantive ones. That distinction, however, seemed to baffle most of the justices. Here's Justice Barrett.

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AMY CONEY BARRETT: Because you do have a problem with explaining why these procedural limitations are OK but substantive limitations are not.

TOTENBERG: Chief Justice Roberts and Justice Kagan both pointed to the court's precedents as problematic for the state Legislature's claim of exclusive power over elections. Roberts noted that the U.S. Supreme Court, nearly a century ago, unanimously upheld laws giving governors power to veto election laws passed by the legislature. Ultimately, Justice Sotomayor grew so impatient with lawyer Thompson's argument that she let fly this comment.

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THOMPSON: I'm done, Your Honor.

SONIA SOTOMAYOR: Yes, if you rewrite history, it's very easy to do.

THOMPSON: I'm not rewriting...

TOTENBERG: Lawyer Neal Katyal, representing groups of North Carolina voters, told the justices that the founders did not envision an all-powerful state legislature unconstrained by courts and governors.

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NEAL KATYAL: Frankly, I'm not sure I've ever come across a theory in this court that would invalidate more state constitutional clauses as being federally unconstitutional - hundreds of them, from the founding to today. The blast radius from their theory would sow elections chaos, forcing a confusing two-track system, with one set of rules for federal elections and another for state ones.

TOTENBERG: For the most part, the argument eventually centered on how to let states do what they've always done - decide issues involving their own state constitutions - but with some constraints. Chief Justice Roberts referred to the provision of the North Carolina Constitution requiring a system of free and fair elections.

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JOHN ROBERTS: Do you think the phrase fair and free elections is providing standards and guidelines?

TOTENBERG: Yes, replied lawyer Katyal. And indeed, some of those provisions are analogous to general provisions in the federal Constitution, like the right of free speech or equal protection of the law, he said.

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KATYAL: So the idea that you could just nullify those by saying they're too abstract is really problematic.

TOTENBERG: Following Katyal to the lectern was lawyer Donald Verrilli, representing the governor and other state officers who oppose what they see as a naked power grab by the state Legislature. He was pressed for a standard that would allow state courts to decide state constitutional questions but have some limits - or, as Justice Alito put it...

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SAMUEL ALITO: Is your standard a standard that can be flunked?

TOTENBERG: Yes, replied Verrilli, but it would have to be...

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DONALD VERRILLI: ...A naked declaration that an act of a legislature under a free and fair elections clause is unfair without any grounding in history or precedent.

TOTENBERG: A decision in the case is expected by summer.

Nina Totenberg, NPR News, Washington. Transcript provided by NPR, Copyright NPR.