Judge Barbara Bellis ruled Thursday that a federal law protecting gun-makers from lawsuits does not prevent lawyers for the families of Sandy Hook victims from arguing that the AR-15 semi-automatic rifle is a military weapon and should not have been sold to civilians.
A lawyer for the families had argued there is an exception in federal law that allows litigation against companies that know, or should know, that their weapons are likely to be used in a way that risks injury to others.
Twenty children and six educators were killed in the December 2012 shooting.
The sides are due back in court Tuesday.
CBS affiliate WFSB reports that lawyer Josh Koskoff, who represents the families, welcomed the news.
"We are thrilled that the gun companies' motion to dismiss was denied. The families look forward to continuing their fight in court," Koskoff said.
Democratic presidential candidate Bernie Sanders has been criticized for his stance on the lawsuit. Sanders told the New York Daily News that "No, I don't" believe that the victims of gun violence should have the ability to sue the gun manufacturer."
Meanwhile on Tuesday, a judge ruled on releasing the Newtown shooter's thoughts on serial killers.
State police don't have to release documents belonging to Newtown elementary school gunman Adam Lanza that were seized from his home.
Judge Carl Schuman overturned a decision made last year by the state Freedom of Information Commission, which ordered state police to turn over the documents to The Hartford Courant under a public records request. The ruling on Friday was first reported by the Republican-American.
The requested materials included a spreadsheet ranking mass murders and a notebook titled "The Big Book of Granny," which contains a story Lanza wrote in fifth grade about a woman who has a gun in her cane and shoots people and another character who likes hurting people, especially children.
The judge ruled that state law shields from public disclosure all seized property not used in criminal prosecutions.
The judge wrote that his decision would be an important one because it will apply to all future cases in which public disclosure is sought for private personal documents not used in criminal trials that police have seized from victims, witnesses and suspects, including diaries, medical records and phone records.
"Exposure of these items to the public when the state has not seen a need to do so in the criminal case entails a significant invasion of the owner's privacy and interference with his or her property rights," the judge wrote.
The Freedom of Information Commission had ruled that Lanza's belongings were public records and were not exempt from disclosure. State public safety officials and prosecutors appealed the decision to Superior Court.
The executive director of the Freedom of Information Commission, Colleen Murphy, declined to comment on the judge's ruling. She said the commission will consider whether to appeal.
The publisher and editor-in-chief of the Courant, Andrew Julien, said the newspaper is "disappointed in the decision" and is assessing its options.