President Barack Obama had vetoed a bill to allow the relatives to file suit against Saudi for its alleged backing of the attackers.
However, Congress have now voted overwhelmingly in favour of reversing his decision – giving Obama the first veto override of his presidency.
Both the House and Senate voted decisively to reverse his decision to throw out the legislation, with Democrats in both chambers abandoning the president in large numbers.
The Senate voted 97-1. The House vote a few hours later was 348-77.
This comes despite emphatic warnings from Obama and top national security officials that flaws in the bill could put US interests, troops, and intelligence personnel at risk.
He then added that the country provides the US with significant amounts of information to help foil terrorist plots.
‘It would be an absolute shame if this legislation, in any way, influenced the Saudi willingness to continue to be among our best counter-terrorism partners,’ he said.
But lawmakers who supported the bill said their priority was the victims of 9/11 and their families, not Saudi Arabia.
‘The White House and the executive branch are far more interested in diplomatic considerations,’ Democrat Senator Chuck Schumer said. ‘We’re more interested in the families and in justice.’
After senators overturned Obama’s veto, White house spokesman Josh Earnest called the vote the ‘single most embarrassing thing’ the Senate has done in decades.
And despite voting to reverse the president’s decision, a group of senators did acknowledge that defects in the bill could open up a legal Pandora’s box.
That is, it could trigger lawsuits from people in other countries seeking redress for injuries or deaths caused by military actions in which the US may have played a role.