"I can identify him, and I'll have him arrested," DeCosta said Monday. "We're not fooling around. This is a post-terrorism environment."
DeCosta said he will use the first day the new law takes effect to declare Hartsfield-Jackson a "gun-free" zone.
He and Franklin plan a 10 a.m. news conference to discuss the new gun law.
"They are not appropriate once you go past security," he said. "But in parking lots or restaurants or public transportation, they are OK."
"He can then have all the NRA [National Rifle Association] lawyers say why it's OK for him to bring a gun to the airport," DeCosta said.
"This license must be carried at any time that an individual is carrying a firearm on MARTA," the statement said.