Striding from the US supreme court to the nearby US Capitol, holding aloft a sign that said “My body my choice” and “Women’s right to choose”, Taylor Treacy was struggling to fathom how she had fewer constitutional rights now than when she awoke that morning.

“It’s heartbreaking,” said the 28-year-old, who works in sports marketing. “The people who have legally gotten abortions in the United States are mostly Black and brown women, yet the five justices able to have the final word were four powerful men and one white woman. We’re allowing more access to guns yet we’re taking away the rights of women. It just seems like we’re going backwards.”

Millions of women had just lost access to abortion on Friday after America’s highest court overturned a near-50-year-old ruling and other precedents enshrining that right. The conservative justice Samuel Alito wrote in the court’s majority opinion that Roe v Wade was “egregiously wrong and deeply damaging”, and that states should decide whether to limit or criminalise the procedure.

The court’s liberal minority responded: “With sorrow – for this Court, but more, for the many millions of American women who have today lost a fundamental constitutional protection – we dissent.” The ruling is expected to lead to abortion bans in roughly half the states, although the timing of those laws taking effect varies.

The decision, though widely expected a draft opinion leaked last month, was nevertheless a stunning aftershock of Donald Trump’s presidency and sure to enflame America’s divisions. It also cemented the supreme court’s emergence an alternative centre of power that threatens to rupture the delicate governing balance of executive, legislature and judiciary.

Just 24 hours earlier, the justices had struck down New York state’s limits on carrying concealed handguns in public, potentially opening the way to fresh legal challenges to other state-level gun laws despite recent mass shootings in California, New York and Texas. It was a triumph for the gun lobby and a blow to Joe Biden’s efforts to curb violence.

Simon Schama, a leading historian, tweeted on Friday: “American democracy is in deep trouble. It can’t survive in its present form if the constitution is manipulated to impose minority rule.”

The back-to-back decisions were the fruit of a long campaign by conservatives to shift the judiciary to the right, powered by influential groups such as the Federalist Society and the Heritage Foundation. The Republican presidents George HW Bush and George W Bush appointed Clarence Thomas, John Roberts (now chief justice) and Alito to the supreme court.

A democratic deficit opened when Senate Republicans blocked Barack Obama’s last nominee for the court, Merrick Garland, on the spurious grounds that it was an election year. Then Trump, a one-term president who had lost the national popular vote by 3m, appointed three justices: Neil Gorsuch, Brett Kavanaugh and Amy Coney Barrett. It has proven his most significant legacy.

The court struck down Roe v Wade against the wishes of a Democratic president, Democratic-controlled Congress and the citizenry. The majority of Americans (61%) believed that Roe should remain the law of the land, and only 36% supported overturning it, according to the Public Religion Research Institute thinktank. Even most religious Americans wanted to see Roe upheld.

Edward Fallone, an associate professor at Marquette University Law School in Milwaukee, Wisconsin, said: “I’m afraid it’s extremely undemocratic. You now have the least democratic branch of the federal government on an ideological agenda to roll back liberties that are extremely popular with the general public in America.

“It is a recipe for potential unrest, certainly demonstrations and political turmoil, as they seem intent on a course of action that will run counter to the will of the public.”

The surge of judicial activism has knocked both the White House and Congress back on their heels. In Washington abortion rights protesters crowded outside the fenced-off supreme court on Friday, opposite the gleaming dome of the US Capitol, where their elected representatives vented frustration at the demise of Roe but were powerless to intervene.

Two miles away at the White House, even the president seemed politically impotent. A solemn group of female staff, including domestic policy adviser Susan Rice and press secretary Karine Jean-Pierre, gathered beneath a staircase in the cross-hall to watch Biden deliver a response. Portraits of Bill Clinton and George W Bush, presidents in an era when Roe seemed sacrosanct, looked on from opposing walls.

Calling it “a sad day for the court and the country”, Biden said: “It was three justices named by one president – Donald Trump – who were the core of today’s decision to upend the scales of justice and eliminate a fundamental right for women in this country.

“Make no mistake: this decision is the culmination of a deliberate effort over decades to upset the balance of our law. It’s a realisation of an extreme ideology and a tragic error by the supreme court, in my view.”

He added: “With this decision, the conservative majority of the supreme court shows how extreme it is, how far removed they are from the majority of this country. They have made the United States an outlier among developed nations in the world.”

The president admitted that he cannot take executive action to secure a woman’s right to choose. The only hope is for Congress to restore the protections of Roe v Wade as federal law, which in turns depends on Democrats winning the midterm elections. “This fall, Roe is on the ballot,” he said. “Personal freedoms are on the ballot.”

Others argue that there is another solution to offset minority rule: expanding the supreme court beyond its current total of nine justices. The pressure group Demand Justice pointed to this week’s rulings on guns and abortion as proof that reform is needed.

Christopher Kang, its co-founder and chief counsel, said: “This is part of the decades-long Republican agenda to accomplish through the supreme court what they cannot through the democratically elected branches of Congress. We’ve seen in the last couple of days decisions making it harder for lawmakers to combat gun violence in the wake of some of the worst mass shootings in our country’s history. We’ve seen, now, overturning the right to an abortion.

“These are things that are supported by 70 to 80% of the American people and I think we’ll see it again next week in a big case concerning whether or not the Environmental Protection Agency has the authority to take action to fight climate change, another thing supported by 70 to 80% of the American people. This is a further example of what Republicans are doing through our unaccountable courts that they couldn’t do through Congress or the White House.”

Americans’ faith in the supreme court has dropped to a historic low, with only 25% saying saying have “a great deal” or “quite a lot” of confidence in it, down from 36% a year ago, according to a Gallup poll. Kang believes that rebuilding trust is crucial to the health of America’s increasingly fragile democracy.

“Today’s ruling shows that the supreme court is the problem and so any solution has to address the supreme court,” he added. “There are other things that the president can do or Congress, with greater majorities, could do but fundamentally we have to fix the court if we have any hope of addressing these problems.”

The calls take on even greater urgency because of what might be to come. Thomas wrote in a concurring opinion on Friday that the supreme court should reconsider other legal precedents protecting same-sex relationships, marriage equality and access to contraception. Biden warned: “This is an extreme and dangerous path this court is taking us on.”

Cristina Tzintzún Ramirez, president of NextGen America, an organisation that works to engage young voters, said: “It is the takeover of an extreme rightwing minority that seeks to roll back the gains for the LGBTQ community, for women, for people of colour.

“This isn’t the end, this is the opening salvo, and they made that clear in their decision. You had Clarence Thomas state they are going to take a look at how they can change the fundamental rights that the LGBTQ community has recently won in this country.”

Ramirez added: “We didn’t defeat fascism in 2020; we beat it back. But to kill fascism in this country is going to require a lot more than one election cycle.”

Friday’s decision is set to create a patchwork of laws from state to state. Twenty-six are certain or likely to immediately ban abortion, according to the Guttmacher Institute thinktank. In Alabama, the state’s three abortion clinics stopped performing the procedure for fear providers would now be prosecuted under a law dating to 1951; women in the waiting room on Friday morning were suddenly turned away. Democratic state governors, however, promised to strengthen protections.

Back at the supreme court, the sun was shining but the mood was one of sombre defiance as hundreds of people waved placards, chanted slogans such as “the supreme court is illegitimate” and contemplated a leap into the unknown after half a century.

At 43, Tracy Tolk, a climate change and energy policy advocate, had known nothing but Roe her entire life. “I’m absolutely devastated,” she said. “I thought it would hurt less because we had a preview but it hurt more than I expected. It’s gut-wrenching. People marched on the Capitol for less than this.”

Virginia Shadron, 71, a retired academic administrator from Stone Mountain, Georgia, was wearing a badge with the face of late liberal justice Ruth Bader Ginsburg, whose death in 2020 allowed Trump to rush through the appointment of Barrett even with a presidential election already under way.

She said: “Millions of women will die. It sets back women and it’s only the beginning. It’s the beginning of the end of many things, as Clarence Thomas said. Next, they’ll take on contraception. Reasonable people can feel strongly and differently about abortion. I’m glad for myself, I never had to make the choice, but if I had needed to, I would have wanted a safe, legal procedure.”

There was sadness in the eyes of Maureen John, 67, who warned that the decision to overturn Roe would lead to an increase in illegal and unsafe abortions. “I’m a nurse and I’ve seen many unnecessary deaths because of the abortions done illegally,” she said.

John was born in Guyana, moved to the US in 1976 and lives in Atlanta, Georgia. “I’m from the Caribbean and I came here and I became an American citizen because of democracy which wasn’t available in my country at that time. I loved it. I love being American and now I’m being disappointed at what’s happening.”

“They’re making a mockery of democracy.”