In her decision granting the company's motion to strike the case, Superior Court Judge Barbara Bellis invoked a federal statute known as PLCAA
, the Protection of Lawful Commerce in Arms Act.
The law prohibits lawsuits against gun manufacturers and distributors if their firearms were used in the commission of a criminal act.
The families had sought
an exemption through a claim of "negligent entrustment," arguing the maker knowingly marketed and sold the Bushmaster AR-15 rifle to civilians despite knowing it posed a risk when used outside "highly regulated institutions" such as law enforcement or the military. Remington is the parent company of Bushmaster.
Bellis said the "criminal misuse of a weapon" by Adam Lanza means the action "falls squarely within the broad immunity provided by PLCAA," adding that the arguments presented by the families do not fit within the definition of negligent entrustment.
Joshua Koskoff, an attorney for the families, said in a statement that his clients plan to appeal.
"While the families are obviously disappointed with the judge's decision, this is not the end of the fight. We will appeal this decision immediately and continue our work to help prevent the next Sandy Hook from happening," he said.
U.S. Sen. Chris Murphy of Connecticut, a prominent voice in the fight for gun control, tweeted: "Disappointed by decision to dismiss the lawsuit brought by #SandyHook families. #PLCAA denies victims of gun violence their day in court."
On December 14, 2012, Lanza fatally shot his mother and then drove to an elementary school in Newtown, Connecticut, where he used the rifle to shoot to death 20 children and six adults. Lanza, 20, killed himself as police approached.
The ruling comes a week after the same judge ordered Remington to continue providing discovery materials to the families' attorneys.
CNN has reached out to Remington for comment. It has previously said the 2005 law provides it "complete immunity."
Sandy Hook was the third-deadliest mass shooting
in the United States. The Pulse nightclub shooting in June 2016 left 49 people dead and the April 2007 Virginia Tech shooting had a death toll of 32.