A US judge in New York dismissed Saudi Arabia's request to dismiss lawsuits accusing Riyadh of helping in the 9/11 attacks.
The cases are based on "Jasta", a 2016 law which provides an exemption to the legal principle of sovereign immunity, allowing families of the victims to take foreign governments to court.
The families point to the fact that majority of hijackers were Saudi citizens, and claim that Saudi officials and institutions "aided and abetted" the attackers in the years leading up to the 9/11 attacks, court documents say.
Riyadh and its Gulf allies had strongly opposed the law, which was initially vetoed by then-President Barack Obama. The US Senate overturned the veto by overwhelmingly adopting the legislation.
Wednesday's ruling comes during Saudi Crown Prince Mohammed bin Salman's visit to the US. President Donald Trump heaped praise on the Saudi royal during a meeting at the White House last week.
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