The court said the two American companies were protected by a law passed by Congress in 2005, the Protection of Lawful Commerce in Arms Act.
But the court said a third company, Beijing-based China North Industries Corp., or Norinco, was not protected by the law because it was not federally licensed. The panel said the lawsuit could proceed against that firm.
The case stemmed from a rampage in which white supremacist Buford Furrow wounded five people, including three children, at a Jewish Community Center in Granada Hills and then killed a Filipino-American postal worker, Joseph Ileto, in Chatsworth on Aug. 10, 1999.
Furrow later pleaded guilty to 16 federal charges including committing a hate crime and was sentenced to life in prison without parole.
Meanwhile, the surviving victims and Ileto's mother sought to sue Georgia-based Glock Inc., RSR Wholesale Guns Seattle Inc. and Norinco for allegedly marketing the guns in a way that encouraged illegal purchasers to buy them.
In an earlier ruling in 2003, the appeals court said the plaintiffs could sue the companies on the common-law claims of creation of a public nuisance and marketing negligence.
But partly in response to that ruling, Congress two years later enacted the Protection of Lawful Commerce in Arms Act, which insulates federally licensed manufacturers and distributors from civil lawsuits if they follow applicable state and federal laws.
The appeals court said in today's ruling that Congress clearly intended to pre-empt common-law claims such as the public nuisance argument.
The court also by a 2-1 vote upheld the constitutionality of the law.