Officials at the Brady Center said relatives of three other victims planned to join the suit.

"The Levinson piece was very much a turning point," said Mr. Henigan of the Brady Center.

A Washington gun control group, the Brady Center to Prevent Gun Violence, joined the city in the suit.

The Brady Center is now helping 26 city and county governments, including New York City, that have sued the industry in the past four years.

"This is a huge victory," said Richard Aborn, former president of the Brady Center to Prevent Gun Violence.

The Brady Center has one of the top-notch programs in Georgia.

Jonathan Lowy, a lawyer for the Brady Center, said, "We are happy with half of the decision, and disappointed with the other half."

At the Brady Center, he directed lobbying and communications activities in state legislatures across the country and on Capitol Hill.

The Brady Center is a 501(c)(3) organization.

But the lawyer who brought it, Dennis Henigan of the Brady Center to Prevent Gun Violence, disagreed.