When America’s highest court ended the constitutional right to abortion after half a century, Jeff Landry, the attorney general of Louisiana, knew whom he wanted to thank.

“This is the day the Lord has made; let us rejoice in it and be glad,” he said in an official statement. “Today, along with millions across Louisiana and America, I rejoice with my departed mom and the unborn children with her in Heaven!”

The southern state’s top law enforcement official was not the only Republican to reference God while taking a victory lap. Nor was he alone in rooting for the supreme court to continue a pattern of forcing religion back into the US political system and tearing down the wall that separates church from state.

The court – said to be more pro-religion than at any time since the 1950s – wrapped up one of its most consequential and divisive terms this week. Critics lamented a string of decisions that they say undermine legal traditions that prevent government officials from promoting any particular faith.

In May the conservative majority ruled in favor of a Christian group that wanted to fly a flag emblazoned with a cross at Boston city hall under a programme aimed at promoting diversity and tolerance among the city’s various communities.

Last month they endorsed taxpayer money paying for students to attend religious schools under a Maine tuition assistance programme in rural areas lacking nearby public high schools.

Then they backed an American football coach at a Washington state public high school who was suspended by a local school district for refusing to stop leading Christian prayers with players on the field after games. This ruling cast aside a 1971 precedent, known as the Lemon test, which took into account factors such as whether the challenged government practice has a secular purpose.

In all three cases, the court decided against government officials whose policies and actions were taken to avoid violating the constitution’s first amendment prohibition on government endorsement of religion, known as the “establishment clause”.

In addition, although their decision last week to overturn the 1973 Roe v Wade ruling that legalised abortion nationwide did not involve the establishment clause, it was celebrated as a seminal victory by religious conservatives. Mike Pence, the former vice-president and a born again Christian, called for a national ban on the procedure.

Paradoxically, the trend comes against the backdrop of an increasingly diverse and secular nation.

Last year a Gallup survey revealed that Americans’ membership in houses of worship dropped below 50% for the first time, and last month Gallup found that the share of US adults who believe in God – 81% – was the lowest since it first asked the question in 1944.

White Christians represented 54% of the population when Barack Obama first ran for president in 2008 but now make up only 45%. Former president Donald Trump’s appointment of three rightwing justices, however, helped put the court on a very different track. And the nature of its rulings have been unusually radical and sweeping.

Robert P Jones, founder and chief executive of the Public Religion Research Institute thinktank in Washington, said: “What we’re seeing is a desperate power grab as the sun is setting on white Christian America. In the courts, instead of moving slowly and systematically, it’s a lurch.”

Jones added: “In the meantime we’re going to be left with essentially an apartheid situation in the US where we’re going to have minority rule by this shrinking group that’s been able to seize the levers of power, even as their cultural democratic representation in the country shrinks.”

The establishment clause prevents the government from establishing a state religion and bars it from favoring one faith over another. Thomas Jefferson, the third president, said in an 1802 letter the provision should represent a “wall of separation” between church and state.

Some far-right Republicans now brazenly challenge that premise. The Colorado congresswoman Lauren Boebert reportedly told a church service last Sunday: “I’m tired of this separation of church and state junk that’s not in the constitution. It was in a stinking letter, and it means nothing like what they say it does.”

In its trio of provocative decisions over the past two months, the supreme court decided that government actions intended to maintain a separation of church and state had instead infringed separate rights to free speech or the free exercise of religion, also protected by the first amendment.

In the ruling on school football coach Joseph Kennedy, the conservative justice Neil Gorsuch wrote that the court’s aim was to prevent public officials from being hostile to religion as they navigate the establishment clause. “In no world may a government entity’s concerns about phantom violations justify actual violations of an individual’s first amendment rights,” Gorsuch opined.

Rachel Laser, president of Americans United for Separation of Church and State, which represented the school board in the case, said the separation was “under complete attack” by the supreme court as it favours the free exercise clause at the expense of the establishment clause, thereby raising the specter of religious favoritism.

“We are at risk of taking away the religious freedom of vast numbers of Americans, which should make the founders of our country be doing somersaults in their grave and I’m sure is alarming to the world as a whole, because they see America as a beacon of light when it comes to religious freedom.”

The line between church and state has been crucial, Laser argues, to advances in LGBTQ equality, racial justice, reproductive freedom, protecting religious minorities, the teaching of science in schools and safeguarding democracy itself. But all this is suddenly precarious because of the court’s 6-3 conservative majority.

She added: “The court pandered to a religious extremist agenda and implemented it by forcing one set of religious views on all of us and taking away the right of a woman to do with her body what her religious and moral views dictate, or taking away the right of a Maine taxpayer to not fund the teaching of a religion or religious discrimination that they disagree with, or taking away the right of a Jewish or Muslim or an atheist or a Buddhist public school student not to feel pressured to pray to play and be included in public school.”

Like Jones, Laser perceives in the court’s opinions a backlash against America’s religious pluralism, racial diversity, an increase in women’s power in society and the advent of marriage equality and progress on LGBTQ equality.

“This is a backlash that is meant to reinforce and cement existing power structures into our law, and it panders to a white Christian right extremist agenda. It’s incredibly divisive. It’s dangerous to our democracy in that regard.”

Unusually, the nine-member supreme court currently includes six Catholics: Chief Justice John Roberts, Samuel Alito, Amy Coney Barrett, Brett Kavanaugh and Clarence Thomas, all appointed by Republican presidents, and Sonia Sotomayor, seated by a Democrat. Last year the court ruled that a Catholic social services agency in Philadelphia could ignore city rules and refuse to work with same-sex couples who apply to take in foster children.

But although most of the court’s religious rights decisions in recent years involved Christian plaintiffs, it has also backed followers of other religions. These included a Muslim woman in 2015 denied a retail sales job because she wore a headscarf for religious reasons and a Buddhist death row inmate in 2019 who wanted a spiritual adviser present at his execution in Texas.

The court also sided with both Christian and Jewish congregations in challenges based on religious rights to governmental restrictions such as limits on public gatherings imposed as public safety measures during the coronavirus pandemic.

The New York Times reported recently: “Since John Roberts became chief justice in 2005, the court has ruled in favor of religious organizations in orally argued cases 83% [now 85%] of the time. That is far more than any court in the past seven decades – all of which were led by chief justices who, like Roberts, were appointed by Republican presidents.”

The shift has been welcomed by conservative pressure groups. Carrie Severino, president of the Judicial Crisis Network, said: “The court’s recent pro-religious liberty streak shows how far it has come from earlier decades. A majority of the justices continue to demonstrate a clear record of protecting religious liberty and expression, something the constitution explicitly guarantees.”

Activists and academic experts, however, warn that the emboldened supermajority of six justices is out of kilter with the will of the people on government endorsement of religion and other issues.

Amanda Hollis-Brusky, an associate professor of politics at Pomona College in Claremont, California, said: “It’s paradoxical but it’s also a function of our system that creates so many avenues for minority rule and that’s something that we as Americans need to really reckon with: whether this 18th-century system still works for us in the 21st century.”