(CNN) The Connecticut Supreme Court ruled Thursday that families of Sandy Hook victims can continue their yearslong lawsuit against gun manufacturers.
The decision says that the families may pursue one of their specific claims in the case: that Remington, the manufacturer of Bushmaster's version of the AR-15 rifle used during the 2012 Sandy Hook Elementary School massacre, knowingly marketed the gun for use by people to "carry out offensive, military style combat missions against their perceived enemies."
State law does not permit advertisements that encourage criminal behavior, according to the decision.
CNN has reached out to Remington and Camfour, a gun distributor named in the case, for comment and has not received a response.
"The families' goal has always been to shed light on Remington's calculated and profit-driven strategy to expand the AR-15 market and court high-risk users, all at the expense of Americans' safety. Today's decision is a critical step toward achieving that goal," said Josh Koskoff, one of the attorneys for the families, in a statement.
The ruling reinstating the lawsuit came after approximately 15 months of judicial deliberations and approximately five years after 10 families initially filed the case, spurred by the massacre that left 26 people -- mostly young children -- dead at Sandy Hook Elementary School in Connecticut in December 2012. Adam Lanza, the gunman, used the Bushmaster gun at the center of this case.
In 2016, a lower-court judge dismissed the case in response to a request by Remington, citing a federal statute that protects gun manufacturers and distributors from being implicated if their weapons are used in criminal activity.
The Sandy Hook families had focused on a portion of their argument against Remington on "negligent entrustment," essentially saying that the company sold guns to civilians knowing they are dangerous outside of certain institutions like the military. But the state Supreme Court said that this angle of the case is not feasible legally.
In allowing the marketing argument to go forward, the justices wrote that their interpretation of the federal statute does not give gun companies free reign to use "truly unethical and irresponsible marketing practices."
In their original complaint, the families outlined some of the marketing practices allegedly used by Bushmaster.
"The Bushmaster Defendant's 2012 Bushmaster Product Catalog shows soldiers moving on patrol through the jungles, armed with Bushmaster rifles," the lawsuit reads. "Superimposed over the silhouette of a soldier holding his helmet against the backdrop of an American flag is text that reads 'when you need to perform under pressure, Bushmaster delivers.'"
The court, echoing claims by the families, emphasized the lethality of the AR-15 style rifle, saying that it is designed to "deliver maximum carnage with extreme efficiency."
"That lethality, combined with the ease with which criminals and mentally unstable individuals can acquire an AR-15, has made the rifle the weapon of choice for mass shootings, including school shootings," the decision says.
Remington attorneys previously argued that the Protection of Lawful Commerce in Arms Act protects companies involved in the sale of the gun that ended up in Lanza's hands from this exact kind of lawsuit. Attorney James Vogts stated in 2017 that the lawsuit would require a reinterpretation of the law itself.
"No matter how tragic, no matter how much we wish those children and their teachers were not lost, their families had not suffered, the law needs to be applied dispassionately," Vogts said in court. "Under the law ... the manufacturer and the sellers of the firearm used by the criminal that day are not legally responsible for his crimes and the harm that he caused."
Importantly, the decision does not rule on whether Remington engaged in this practice. The Sandy Hook families will still need to argue this theory in Bridgeport Superior Court, where the case will return after the ruling.
"...[It] falls to a jury to decide whether the promotional schemes alleged in the present case rise to the level of illegal trade practices and whether fault for the tragedy can be laid at their feet," the decision reads.
Parents involved in the lawsuit said a jury needs to look at advertising for the gun and Remington documents and emails about its marketing.
"I can't say I was excited by this ruling," said Ian Hockley, father of Sandy Hook victim Dylan Hockley, 6. "I wish it was never here, but what we've said from the onset is all we want is our day in court, for the law to be upheld and for a jury to decide our case. "