What is this ruling all about?

At face value, Louisiana v Callais focuses narrowly on Louisiana’s congressional maps. Lawmakers, abiding by existing law, had drafted maps that included two majority-Black districts out of six – roughly proportionate to the state’s population which is one-third African American.

A group of white voters sued, arguing that drawing maps specifically based on race was unlawful discrimination under the US constitution. The supreme court majority agreed with them.

The ruling dramatically changes the terms of a key provision within the Voting Rights Act known as section 2. From now on, a state’s maps can only be challenged where it can be shown that there was intentional racial discrimination.

That is a very difficult standard to prove, and one that Congress has for almost half a century specifically avoided. In a one-two punch, the ruling also says that race may no longer be considered when proposing alternative maps.

Viewed from the longer arc of American history, Wednesday’s ruling is vast. It effectively guts a final pillar of the Voting Rights Act, which for decades has been used to safeguard the political power of Black and other minority voters.

It is the latest serious blow to the Voting Rights Act to come from supreme court conservatives, stretching back to Shelby county v Holder in 2013. The court has piecemeal eviscerated a legendary statute that was passed in 1965 following years of bloody struggle and has been hailed the crown jewel of the civil rights movement.

What did it mean for voting rights protections?

For decades, section 2 has acted as a central shield for minority voters in largely southern states that have relentlessly resisted granting them equal political influence. Until Wednesday’s ruling, the law could be invoked to block maps that had the effect of depriving Black voters of proportionate electoral power.

Now that protection has been stripped from them.

Under the new ruling, anyone challenging a state’s maps will have to prove that the lawmakers were motivated by a desire to racially discriminate against minority voters, and not just by a wish to gain partisan party political advantage. That requires disentangling race from party preference, which is virtually impossible given the enduring loyalty of Black voters to the Democratic party.

According to the Pew Research Center, 83% of Black voters favor the Democratic party across the US, a proportion that is even higher in the South.

Under the new ruling, all states need to do is insist that their maps are designed with partisan politics in mind, and they will in effect be immune from challenge on grounds of racial discrimination.

How has the ruling been received?

Louisiana’s Republican leaders predictably responded with glee. “We win in Louisiana v Callais!” said the state’s attorney general, Liz Murrill.

But those concerned about civil rights protections have been thrown into despondency. The most vicsceral lament came from the three liberal-leaning justices on the supreme court who were outnumbered by the conservative majority.

In a dissent written by Elena Kagan, and joined by Sonia Sotomayor and Ketanji Brown Jackson, they castigated this week’s ruling as a “demolition” of the Voting Rights Act. It would leave states free to dilute the voting power of minority citizens without legal consequence, with the result that “minority representation in government institutions will sharply decline”.

Could this impact the midterm elections in November?

The supreme court issued its decision notably early – the tradition of the court is to deliver big rulings at the end of its judicial year in late June. That inevitably raises suspicion that the conservative justices wanted to give Republican states sufficient time to act before the midterms.

Several southern states have already begun the process of revising their maps, hours after the ruling came down. They are led by Louisiana itself, which on Thursday postponed its primary elections to allow the state to revert to a single majority district for Black voters.

Several other southern states are similarly scrambling to redraw their congressional districts, secure in the knowledge that they now have supreme court blessing. Trump signaled on Thursday that Tennessee’s governor, Bill Lee, plans to redistrict to gain an extra Republican seat as the party faces possibly losing control of the House of Representatives in November.

The flurry of redistricting that now looks inevitable is highly unusual for mid-decade elections. It comes on top of the frenzy of activity already unleashed by Trump after he urged Texas Republicans to boost their congressional districts.

What are the longer-term implications for minority voters?

The Voting Rights Act emerged from the struggles of the civil rights movement as a means of combatting the virulent racial discrimination that festered under southern Jim Crow laws.

The statute sought to fulfill the promise of the 15th amendment of the US constitution that granted freed enslaved people the right to vote. Until the Voting Rights Act was enacted, the amendment was stymied by a slew of legislative tricks that disenfranchised African Americans, from literacy tests to poll taxes.

It is unlikely that the country will return to the most extreme forms of discrimination that proliferated in those dark days. But as Kagan put it in her dissent, the Voting Rights Act is now all but dead, leaving Black and other minority voters exposed.

They are once again at the whim of Republican leaders free to revive age-old practices in map drawing, such as the colorfully-named “cracking” and “packing”. Such measures are likely to diminish the electoral representation of minority Americans, and with it their political voice.