Photograph: Brendan McDermid/Reuters

The supreme court has declined to rule in a pair of partisan gerrymandering cases, in a demurral that advocacy groups warned could amount to a “green light” for abuse by political insiders in charge of redrawing state legislative maps.

Pro-democracy groups had hoped the court would declare partisan gerrymandering unconstitutional and throw out maps in Maryland, where Democratic mapmakers were accused of shrinking Republican influence by distorting district lines; and in North Carolina, where Republican operatives were accused of doing the same to Democrats.

But the court has deferred in both cases concluding that authority over district maps rests with state legislatures and the US Congress, and not the supreme court.

“Partisan gerrymandering claims present political questions beyond the reach of the federal courts,” Chief Justice John Roberts wrote in a 5-4 opinion for the majority. The ruling split evenly along ideological lines, with the court’s four liberal-leaning justices dissenting.

Justice Elena Kagan’s dissent blasted the court for its diffidence. “For the first time ever, this court refuses to remedy a constitutional violation because it thinks the task beyond judicial capabilities,” she wrote.

Pro-democracy activists warned that the ruling opened the way for more aggressive gerrymandering. “Letting politicians manipulate voting maps is like putting the fox in charge of the henhouse,” the advocacy group Common Cause said in a statement. “Whether they favor Democrats or Republicans, gerrymanders cheat voters.”

For the first time, this court refuses to remedy a constitutional violation because it thinks the task beyond judicial capabilities Elena Kagan

State-level courts would still be able to hear partisan gerrymandering cases, but the supreme court’s demurral meant that no federal standard to block the practice was likely soon.

“Today’s decision is a setback in the fight for fair maps around the country,” said Paul Smith, vice-president at the Campaign Legal Center. “We must redouble our efforts outside the courtroom to keep advancing efforts that put the voices of voters first.”

Story continues

Brian Fallon, executive director of We Demand Justice, tweeted: “This ruling on gerrymandering is exactly why it is not enough to just win the next election. The supreme court is helping Republicans rig the elections. Democrats need a proactive plan to confront the partisan capture of the court.”

Legislative districts in the United States are redrawn after each decennial US census, which captures a picture of how the population of a certain area or state has changed and which can result in the addition or subtraction of districts depending on population fluctuation.

Political operatives on both sides have long seized the chance to redraw maps in ways that give one party an advantage either by herding all voters from the opposite party into a single district or by splitting blocs of voters into multiple districts to diminish their influence.

A wave of citizen advocacy against gerrymandering in recent elections – in Arizona, California, Colorado, Idaho, Michigan, Montana and Washington – has witnessed the creation of independent redistricting commissions for map-drawing. But rules for changing the practice of redistricting vary by state.

“The fight against partisan gerrymandering is a state fight,” Common Cause said. “States must set clear rules to prevent elected officials from drawing unfair maps and stripping voters of their voice – and they have the public support to pass reform.”

Michael Waldman, the president of the Brennan Center for Justice, said: “Chief Justice Roberts’ ruling that no federal court can ever consider claims of extreme and unconstitutional partisan gerrymandering is truly appalling for the long-term health of our democracy. It’s a judicial green light for egregious partisanship, a permission slip for politicians to entrench themselves without fear of judicial intervention.”