The U.S. Supreme Court delivered a landmark decision Wednesday that significantly curtails the use of race in drawing congressional districts, a move that experts warn could reshape the political landscape for decades and result in the largest-ever reduction in Black representation in Congress.

In Louisiana v. Callais, the court's conservative majority voted 6-3 to strike down Louisiana's congressional map that created a second majority-Black voting district. The justices ruled the map constituted an unconstitutional racial gerrymander, significantly weakening Section 2 of the Voting Rights Act, which had limited states from diluting minority voting power through redistricting.

The decision has immediate national implications. Republicans could gain up to 19 U.S. House seats and up to 200 state legislative seats across the South, according to projections by voting rights organizations. While most states lack time to redraw maps before the November midterms, the ruling is expected to trigger a wave of redistricting battles in coming years.

Already, several Republican-led states have moved swiftly. Florida Gov. Ron DeSantis invoked the pending decision to justify a proposed gerrymander aimed at handing Republicans four additional House seats. Tennessee Republican Sen. Marsha Blackburn called for her state legislature to reconvene to create another GOP-held seat in Memphis, while Mississippi Gov. Tate Reeves announced a special session to redraw districts.

Governor Andy Beshear condemned the decision, calling it "a historic blow to the Voting Rights Act" that will prevent millions of Americans, especially Black Americans, from having fair representation. The Democratic governor, who chairs the Democratic Governors Association, urged voters to elect more Democratic governors as a counterweight.

The ruling reflects years of erosion of voting rights protections. Justice Elena Kagan wrote in dissent that under the court's new interpretation, "a State can, without legal consequence, systematically dilute minority citizens' voting power." Legal experts described the decision as potentially transformative. "It is hard to overstate what an earthquake this will be for American politics," said UCLA law professor Rick Hasen.