The US supreme court, in a 5-4 decision, used the ruse that it was too close to an election – three months away – to scrap a racially discriminatory, Republican-drawn legislative map in Alabama. A lower court had previously ruled against the state because its gerrymandered congressional districts diluted the voting strength of African Americans by ensuring that 27% of Alabama’s population would garner only 14% of the state’s congressional representation. But that reality didn’t faze five justices; the US supreme court was just fine with letting a policy designed to disfranchise Black voters unfurl and do its damage in an oncoming federal election.

The echoes of a brutal past are resonating in this decision.

After the civil war, Congress passed the 1867 Reconstruction Act, which provided that Black men had the right to vote, and then Congress followed that with the 15th amendment, which banned states from using race, color or previous conditions of servitude to undermine the right to vote.

In a series of decisions in the late 19th and early to mid-20th centuries, however, the supreme court systematically dismantled those protections, as well as others crafted to support African Americans’ citizenship rights and defend against white domestic terrorism waged by the Ku Klux Klan and similar organizations. Focusing on voting rights gives some indication of how pernicious the decisions were. The 1874 Minor v Happersett ruling asserted that the right to vote was not part and parcel of American citizenship.

In 1876, United States v Reese et al dealt with a Black man who was trapped in a malicious catch-22 that prevented him from voting. He tried to pay his poll tax, which was required to vote, but the tax collector refused to accept the payment and the registrars would not allow him to cast a ballot without payment. The court ruled, despite this crude and brazen denial of his right to vote, that the 15th amendment “does not confer the right of suffrage upon any one”.

As states then began fully implementing Jim Crow legislation to disfranchise African Americans, the court, in the Williams v Mississippi (1898) decision, looked at the poll tax and the literacy test and ruled that those chokepoints to the ballot box – which had already removed 90% of registered Black voters in Mississippi from the rolls – did not violate the 15th amendment.

In a 1903 case out of Alabama, Giles v Harris, the supreme court determined that it was powerless to stop a state from disfranchising Black voters even if the methods were unconstitutional.

This assault on African Americans’ right to vote was an assault on American democracy aided and abetted by the highest court in the land. The results were devastating. By 1960, there were counties in Alabama that had no Black voters registered, while simultaneously having more than 100% of white age-eligible voters on the rolls. In Mississippi a mere 6.7% of eligible Black adults were registered to vote.

It took the blood, the courage and the martyrdom of civil rights workers combined with the political spine of a president and congressional leaders to break this stranglehold on the right to vote. The legislature passed and President Lyndon Johnson signed the Voting Rights Act (VRA), which would save America from its worst self. And, this time, in the late 1960s, the US supreme court came down on the side of democracy and the 15th amendment. Two crucial decisions buttressed the VRA, noting that it was not only constitutional but also created to deal with “the subtle, as well as the obvious, state regulations which have the effect of denying citizens their right to vote because of race”.

The Roberts court, however, bears no resemblance to the one in the 1960s and has all the anti-voting rights earmarks of the court after the civil war. The Roberts court’s assault on the VRA and the 15th amendment has been relentless and brutal to American democracy.

The Shelby County v Holder (2013) decision ended the most powerful tool in the VRA’s wheelhouse, pre-clearance, and allowed states and jurisdictions with a demonstrated history of racial discrimination to implement laws and election policies without the prior approval of the US Department of Justice or the federal court in Washington DC.

Within two hours of that decision, Texas implemented a voter ID law that led district court Judge Nelva Gonzales Ramos to rule that the new measure not only had a discriminatory effect, it also had a discriminatory intent. The state appealed to the fifth circuit, pleading with the judges to not dismantle the voter ID law because it would be too disruptive to the looming midterm election in 2014.

When the case reached the US supreme court, Justice Antonin Scalia’s majority ruled in favor of Texas without comment. Justice Ruth Bader Ginsburg’s dissent, however, tore away at the state’s ruse that it was too close to the midterms to stop a racially discriminatory law in its tracks. The greatest threat to confidence in elections, she wrote, was to allow a “purposefully discriminatory law, one that likely imposes an unconstitutional poll tax and risks denying the right to vote to hundreds of thousands of eligible voters” to be used in a federal election.

But the majority on the US supreme court was fine with letting discrimination run wild in the election system.

That has been abundantly clear in a number of voting rights cases that have come before the Roberts court since the Shelby County v Holder decision. Each one, whether massive voter roll purges in violation of the National Voter Registration Act, extreme partisan gerrymandered districts, or election laws that have a disparate impact on minorities, has been approved, either by acts of commission or omission, by the US supreme court.

There are consequences.

The very legitimacy of the court is at stake. Right now it’s as precariously perched as the right to vote and American democracy. Unfortunately, the Roberts court has played a major, horrific role in this preventable disaster.

• Carol Anderson is the Charles Howard Candler professor of African American studies at Emory University and the author of White Rage: The Unspoken Truth of Our Racial Divide and One Person, No Vote: How Voter Suppression is Destroying Our Democracy. She is a contributor to the Guardian