The long-suffering families of children murdered in the 2012 schoolhouse gun slaughter in Newtown, Conn., won fresh hope in court this week. A Connecticut state judge denied a motion to throw out their lawsuit against the manufacturers of the Bushmaster AR-15, a military-style assault rifle used to kill 20 children and six adults in the grisly siege.

The ruling, though far from a final victory for the plaintiffs, at least allows the civil suit to go forward — no small feat considering the strong shield of immunity from liability that Congress cravenly enacted for the gun industry in 2005. This customized favor for gun makers and dealers is enjoyed by no other American industry. It has been repeatedly upheld in courts where attempts to hold the industry accountable for its role in the nation’s gun scourge have been summarily dismissed.

But the Newtown suit is surviving for now with its novel legal challenge. Nine victims’ families and a teacher wounded in the attack contend Bushmaster Firearms International and Remington Arms should be liable under a “negligent entrustment” exception in the immunity shield. The parents accuse the gun makers of recklessly marketing a lightly adapted weapon of war to civilians who could use it for mass killings. The suit contends the rifle’s value for sporting and self-defense was “negligible in comparison to the risk that the weapon would be used in its assaultive capacity.”