A motion filed by gun companies requesting that a lawsuit brought by 10 families affected by the Sandy Hook school massacre be thrown out was denied by a Connecticut Judge. They had requested to be shielded by a law known as Protection of Lawful Commerce in Arms Act (PLCAA), which protects gun manufacturers from civil lawsuits.
Newsweek reports that the basis of the argument of the 10 plaintiff families is that the rifle shouldn’t have been entrusted to the general public because it is a "military-style assault weapon" that should not have been in the hands of civilians and that the gun companies knew, or should have known, the risk it posed.
The next court date, per Newsweek, is April 19th, at which time the Judge is expected to issue her ruling. This decision, if in favor of the plaintiffs, would potentially open up gun manufacturers to a litany of civil suits and could potentially change protections given to weapons manufacturers nationwide.
The AR-15 rifle is a single shot firearm physically designed to resemble the military grade M-16, however, the AR-15 Bushmaster used by Adam Lanza in the Connecticut shooting was not an automatic firing weapon.
See http://abcnews.go.com/Blotter/newtown-massacre-bushmaster-223/story?id=18000884 for discussion of the weapon used in the Connecticut shootings.
The PLCAA is codified at 15 U.S.C. §§ 7901-7903. See https://www.fas.org/sgp/crs/misc/ R42871.pdf for an explanation of the law.