The gun industry suffered a potentially significant legal setback Thursday when the Connecticut Supreme Court said a leading maker of AR-15 rifles could be held legally responsible for marketing practices that allegedly made the semiautomatic gun the weapon of choice for mass shooters.

In a 4-3 ruling, the court overturned the dismissal of a wrongful-death lawsuit brought by families of victims killed in 2012 at Sandy Hook Elementary School in Newtown, Conn. The suit was brought against Remington Outdoor Co., the maker of the weapon Adam Lanza used to kill 26 people, most of them young children.

The ruling allows the plaintiffs to move forward with claims that Remington’s marketing campaigns violated Connecticut’s consumer-protection law, which prohibits advertising and marketing that is “immoral and unscrupulous.”

The plaintiffs alleged that Remington unlawfully promoted the rifle to young, civilian men as a weapon with awesome power and ideal for combat.

A representative for Remington didn’t respond to requests for comment. Remington had argued the claims were barred by a 2005 federal law that grants the gun industry expansive immunity from liability claims over gun violence. That law, however, has an exception, under which manufacturers may be liable for injuries resulting from violations of state laws dealing with the marketing of their products.