A day after the US election, the Supreme court will determine whether a Catholic adoption agency can exclude gay and lesbian couples from fostering children in the name of its religious beliefs.
It will be the first major hearing to come before Justice Amy Coney Barrett, a devout Catholic appointed by President Donald Trump and sworn in last week over the objection of Democrats.
Her appointment eight days before the presidential vote solidified the court's conservative majority, which now stands at six out of nine justices.
The case will provide the court a new chance to recognise broader religious rights under the Constitution, building on other rulings in recent years.
The court has previously cemented its reputation as favourable to Christian conservatives with rulings that embraced certain federal laws and paved the way for money to go to religious schools.
Religious and LGBT rights collide
LGBT rights advocates said the case has implications not just for same-sex couples, but an array of minorities including those practising other faiths.
In March 2018, the city of Philadelphia learned that one of its child welfare providers, Catholic Social Services (CSS), had refused to match foster children with same-sex couples.
In the resulting case, CSS alleged that the move violated its First Amendment rights guaranteeing freedom of religion and expression under the US Constitution.
"Philadelphia demands that a religious agency, an arm of a church, speak and act according to Philadelphia’s beliefs," the group said in a court brief.
CSS said it will be forced to close if its foster care operations if it's unable to participate in Philadelphia's program.
Its case has received support from dozens of churches and lawmakers from Bible Belt states as well as the Trump administration, which says that the northeast US city is acting out of "hostility" towards religion.
Philadelphia has required all foster partners to sign a non-discrimination clause and argued in its own brief that "the Constitution does not grant CSS the right to dictate the terms on which it carries out the government's work."
The city has received the backing of the liberal American Civil Liberties Union, which warned that the case "could allow private agencies that receive taxpayer-funding to provide government services... to deny services to people who are LGBTQ, Jewish, Muslim or Mormon."
A ruling against Philadelphia could make it easier for citizens to cite religious beliefs when seeking exemptions from relevant laws such as anti-discrimination statutes.
The court will decide on the case in 2021.