How legal tide turned on same-sex marriage in the US
Same sex marriage is now legal in thirty-six US states, covering a majority of the US population.
A critical turning point came in October 2014, when the Supreme Court chose not to hear appeals against lower court rulings that had overturned same-sex marriage bans in five states.
How many US states allow same-sex marriage?
In many other states, same-sex marriage has been approved either through legislation, court rulings or voter referenda.
Other states have passed bans or state constitutional amendments forbidding such unions. Some ban same-sex marriage but recognise couples married in other states.
In that case, the court overturned the 1996 federal Defense of Marriage Act (Doma), which barred the federal government from recognising same sex marriages.
Under Doma, for example, individuals in same-sex marriages were ineligible for benefits from federal programmes such as the Social Security pension system and some tax allowances if their partners died.
They argued that the Supreme Court should strike down a state law, called Proposition 8, which stated that marriage is between a man and a woman. The law, approved by California voters in 2008, overrode a state Supreme Court decision that allowed for same-sex marriage.
The justices, who have previously have stopped short of resolving the question of same-sex marriage nationally, say they will consider whether or not states are constitutionally required to issue marriage licences and if states are required to recognise same-sex marriages performed elsewhere.