Relatives of some of the 26 adults and children killed in the Sandy Hook massacre have been told they can sue the maker of the military assault rifle used in the attack.

In a decision that could have huge ramifications in a country where up to 10,000 people a year lose their lives to gun violence, a judge refused a request by the manufacturer of the weapon to dismiss the lawsuit, and instead ruled that it could proceed.

Judge Barbara Bellis said the federal law protecting gun makers from lawsuits did not override the “legal sufficiency” of the claims by the Sandy Hook families that the gun used by Adam Lanza should never have been made available for sale to civilians.

A bus traveling from Newtown to Monroe stops in front of 26 angels along the roadside on the first day of classes for Sandy Hook Elementary School students since the Dec. 14, 2012 shooting. (AP Photo/Jessica Hill, File)

She said that all sides in the case should return to court on April 19 for a further update, the Connecticut Times said.

The lawsuit was brought by a number of families devastated by the attack on the Connecticut primary school in December 2012. The lawsuit claimed that Remington Outdoor Co, maker of the AR-15 assault weapon, made and sold a military-style weapon without regard for the “unreasonable and egregious risk of physical injury to others.”

The families of 10 victims filed suit against the Remington Arms Company, Camfour Holding LLC, the gun’s distributor and Riverview Sales, the store where Lanza’s mother bought the gun. They claimed the gun maker and sellers knew that civilians are unfit to operate the assault rifle and yet continue selling it to civilians disregarding the threat the gun posed.

The lawsuit also alleged that Remington and the other defendants “unethically, oppressively, immorally and unscrupulously marketed and promoted the assaultive qualities and military uses of AR-15s to civilian purchasers.”

In December 2015, Remington, Camfour and the gun store asked Judge Bellis to throw out the lawsuit, claiming they were immune from the families’ claims under the federal Protection of Lawful Commerce in Arms Act.

“The court concludes that any immunity that PLCAA may provide does not implicate this court’s subject matter jurisdiction,” Ms Bellis ruled in her 18-page decision. “Accordingly, the defendants’ motions to dismiss, in which they claim that the court lacks subject matter jurisdiction, cannot be granted on the basis of PLCAA.”

The Sandy Hook Elementary School building where 26 children and adults were killed (AP Photo/Jessica Hill)

Lanza killed his mother before launching his assault on the school in the villlage of Newtown, killing 20 children aged between 6 and 7. Six teachers were also killed, before Lanza shot himself in the head.

“The AR-15 was designed as a military weapon. Born out of the exigencies of combat, the AR-15 was engineered to deliver maximum carnage with extreme efficiency,” the lawsuit added.

“The AR-15 proved to be very good at its job. It has endured as the US Army’s standard-issue rifle and has more recently become a valuable law enforcement weapon.”

The lawsuit said that the weapon has little utility for legitimate civilian use. It says that its size and firepower mean it is a liability for home defence.

“But there is one civilian activity in which the AR-15 reigns supreme: mass shootings,” it added.

“Time and time again, mentally unstable individuals and criminals have acquired an AR-15 with ease and they have unleashed the rifle’s lethal power onto our streets, our malls, our places of worship and our schools.”

Representatives from Remington, the distributor Camfour Inc, and the East Windsor gun shop that sold the rifle to Nancy Lanza had all requested that the lawsuit be thrown out.

Nicole Hockley, the mother of six-year-old Sandy Hook victim Dylan Hockley, said earlier this year that gun companies “must be held accountable for marketing and selling the AR-15, a killing machine designed only for military use, to violence-prone young men”.