By a 5-4 vote, the court rejected an appeal from Alabama’s Republican lawmakers and said they need to draw a second district to achieve greater equality and to give Black or Latino voters a better chance to elect a candidate of their choice.

The ruling in Allen vs. Milligan is a surprising win for civil rights lawyers. They had argued the voting power of Blacks would be “diluted” and made meaningless if nearly all the districts can be carefully drawn to preserve white majorities.

A ruling for the GOP would have helped Republicans maintain their narrow control of the House of Representatives.

But instead, Chief Justice John G. Roberts joined by the court’s three liberals and by Justice Brett M. Kavanaugh said the Voting Rights Act called for creating a new district that might elect a Black candidate.

In 1982, Congress amended the Voting Rights Act to forbid drawing election districts “in a manner which results in a denial or abridgement of the right… to vote on account of race or color.”

Six of Alabama’s seven congressional districts reliably elect a Republican, although about 27% of the state’s population is Black.

Last year, a three-judge panel ruled the state must redraw its map to create a second compact district with a near Black majority. The judges, including two appointed by President Trump, said the Voting Rights Act required giving Black voters a meaningful opportunity to elect a representative of their choice.

But in a preliminary win for the GOP, the Supreme Court last year blocked that decision from taking effect.

Congress amended the Voting Rights Act in 1982 to require states make an extra effort to ensure that Blacks and Latinos had a fair opportunity “to elect representatives of their choice.” That provision was strongly opposed by Roberts, who was then a young Justice Department lawyer in the Reagan administration.

In response to the amended law, judges agreed states had to consider the race of the voters when drawing new districts.

Doing so often led to partisan conflicts. Republicans said they opposed using race as a factor for drawing election districts, and they said it was not required by the 1982 law or the Constitution. Republican-controlled states also resisted the demand to draw more districts that would elect Black Democrats instead of white Republicans.