The US judge said that the allegations in the New York lawsuit met the requirements for the court to assume jurisdiction under the country's Justice Against Sponsors of Terrorism Act.
A judge on Wednesday rejected Saudi Arabia's motion to end a New York lawsuit seeking to hold it responsible in the September 11 attacks.
In dismissing the motion, US District Judge George Daniels said the plaintiffs' allegations met the requirements for the court to assume jurisdiction under the Justice Against Sponsors of Terrorism Act.
Congress passed the act in 2016 over then-President Barack Obama's veto, allowing the claims to go forward against Saudi Arabia after they were rejected once in the courts.
"This is really a historic day for the families," said Sean Carter, attorney for the plaintiffs. "The families have been trying for many years to have an opportunity for the Saudi government to answer on the merits."
A message seeking comment from lawyers representing the Saudi government was not immediately returned.
Daniels had previously rejected arguments that Saudi Arabia backed the hijackers. In Wednesday's ruling, he also dismissed claims against two Saudi banks and a construction company with ties to Osama bin Laden, saying he lacked jurisdiction.
Hundreds of victims' relatives and injured survivors, along with injured corporations, sued the Saudi government in 2003, saying its employees knowingly assisted hijackers who carried out the attacks and fueled al-Qaeda's development into a terrorist organization by funding charities that supported the group.
Most attackers were Saudis
Fifteen of the 19 attackers were Saudis. The US investigated some Saudi diplomats and others with Saudi government ties who knew hijackers after they arrived in the US, according to now-declassified documents.
The 9/11 Commission report found "no evidence that the Saudi government as an institution or senior Saudi officials individually funded" the attacks al-Qaida masterminded, but the commission also noted "the likelihood" that Saudi-government-sponsored charities did.
The Saudi government has long denied any involvement in the attacks.
At a hearing in January, attorney Michael Kellogg, arguing for Saudi Arabia, cited the report repeatedly, along with the findings of probes by the FBI and CIA.
"All rejected Saudi Arabia was responsible," he said.