The ruling clears the way for a ground-breaking case which could redefine the rules over whether gunmakers can be held accountable for the criminal use of their wares.
The Washington-based Centre to Prevent Handgun Violence brought the case on behalf of families of the victims of a shooting spree in downtown San Francisco in July 1993. Gian Luigi Ferri, who is said to have harboured a grudge against lawyers, walked into the high rise building, produced two TEC-DC9 assault pistols, and sprayed the offices with bullets, killing eight people. He then shot himself.
Judge James Warren, of San Francisco Superior Court, ruled the centre could go ahead with lawsuits it filed last year against Intratec of Miami, maker of the TEC-DC9, despite arguments by Intratec that Ferri's rapid- fire pistols had been legally made and sold outside California.
The decision marks a departure from the view taken by state courts that the responsibility for crimes lies with those who physically commit them.
The centre - chaired by the wife of James Brady, the White House press secretary wounded in an assassination attempt on President Reagan - said that the TEC-DC9 pistol was made for close-range multiple killings.
The TEC-DC9 and high-capacity magazines similar to those used by Ferri are now banned by Congress.