Maps can guide us home. They show us where we are, where we have been and where we might go. Electoral maps can do something even more sinister, though. They often tell us what and who is allowed to matter. They can decide, before a single ballot is cast, whether an entire voting bloc will become powerful or be buried by the design of a party that is indifferent – at best – to their needs and wants.

Memphis is the latest warning. Tennessee’s largest majority-Black city can vote, organize, turn out, remember and resist – and still be cut into pieces by politicians who fear what that city might do with power. This week, Republicans carved up the Memphis-centered congressional district, dividing its only majority-Black district into three Republican-leaning seats while weakening voter-notice requirements in the process.

Gerrymandering, at its most brutal, does more than help one party win. It teaches a community that even overwhelming local political will can be made irrelevant by a map.

The United States may be celebrating 250 years since the Declaration of Independence, but anything resembling a multiracial democracy here is barely older than the Voting Rights Act. The effectively erstwhile Voting Rights Act of 1965 (VRA) was enormously consequential, addressing ballot access, voter registration and the brute mechanics of disfranchisement. It addressed racial vote dilution. It was born from the knowledge that the US, left to itself, would not protect Black political power. It was also incomplete.

Racism remains a shapeshifter, and the old, now-disempowered VRA was not built to combat all of its forms. It was certainly not built for our full modern machinery of electoral mapmaking: the data analyst, the algorithm, the partisan alibi, the lawmaker who knows how to make racial harm speak the language of party politics.

So when the six supreme court conservatives issued the Louisiana v Callais ruling – weakening the VRA section that, for decades, helped prevent states from drawing maps that diluted Black political power – what we lost was not abstract. We lost one of the only federal tools we had against one of the most effective weapons in US politics.

The trap is almost elegant in its cruelty. If a state draws a map that dilutes Black political power, it can insist that it was not........

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