But those opposing the Newtown families argue that the lawsuit is specifically the kind of legal challenge the federal protections were designed to block and that the litigation is simply an effort to use the courts as a forum to regulate gun laws.

Image A Connecticut State Police photo of the AR-15 style Bushmaster rifle used by Adam Lanza in the Sandy Hook massacre, in which 26 people were killed, including 20 children. Credit... Connecticut State Police, via Getty Images

The lawsuit, brought by the families of nine people who were killed and one teacher who was shot and survived, faces significant legal hurdles. It was elevated to the Connecticut Supreme Court after a lower court judge dismissed the lawsuit last year after she found that the claims it raised fell “squarely within the broad immunity” provided by federal law.

Mass shootings across the country have been followed by a flurry of legal action, but lawsuits brought against gun companies have failed after running headfirst into the high bar established by federal law.

In 2005, Congress passed the Protection of Lawful Commerce in Arms Act, which sharply restricted lawsuits against gun sellers and makers by granting industrywide immunity from blame when one of their products is used in a crime. Lawmakers behind the measure cited a need to foil what they described as predatory and politically driven litigation. But the law does allow exceptions for sale and marketing practices that violate state or federal laws and instances of so-called negligent entrustment, in which a gun is carelessly given or sold to a person posing a high risk of misusing it.

Legal experts said negligent entrustment has been cited with some success in lawsuits against gun dealers, but the Newtown families are for the first time broadening the scope to include a weapon’s manufacturer, in this case, Remington, which, along with a wholesaler and a local retailer, are all named in the suit. The companies’ lawyers declined to comment.

On Dec. 14, 2012, Adam Lanza, a troubled 20-year-old, stormed into Sandy Hook Elementary School armed with an AR-15 style Bushmaster rifle, firing 154 rounds in less than five minutes. The weapon had been legally purchased by his mother, Nancy Lanza, whom he also killed.