The Supreme Court's ruling that two North Carolina congressional districts relied too heavily on race should give voting-rights advocates a potent tool to fight other electoral maps drawn to give Republicans an advantage in the state.

The justices agreed Monday with a federal court that had struck down two congressional districts as illegally race-based. Because those districts were already redrawn for the 2016 election, the ruling doesn't require immediate changes from North Carolina. But it looms large in other battles unfolding over voting districts there and elsewhere.

Also pending before the high court is a separate challenge to North Carolina state House and Senate districts that have helped the GOP cement veto-proof majorities in both chambers.

A lawyer challenging the General Assembly districts said legislative mapmakers used similar reasoning to defend the congressional and legislative maps, so Monday's ruling bolsters her cause.

"It's abundantly clear that what the state of North Carolina did in drawing its legislative districts cannot withstand constitutional muster," Anita Earls of the Southern Coalition for Social Justice said in a phone interview.

In the case Earls is arguing, a federal court had previously thrown out 28 state House and Senate districts as illegal racial gerrymanders. But earlier this year the Supreme Court temporarily halted an order to redraw those legislative districts. The justices could act on the challenge to the state districts as early as next week.

In recent years, the Supreme Court has ruled for civil rights groups and black voters in challenges to political districts in Alabama, North Carolina and Virginia.

A Democratic group led by former Attorney General Eric Holder is focusing on redistricting challenges to counter political gains Republicans have made since the 2010 census and the redrawing of electoral districts that followed.