The Federal Bureau of Alcohol, Tobacco and Firearms revoked David LaGuercia's license on December 20, and the 60-day appeal window has now expired.
ATF spokeswoman Deb Seifert would not elaborate on the reasons for revoking LaGuercia's license, but confirmed to the Westchester County, N.Y. Journal News the action was permanent.
LaGuercia owns Riverview Gun Sales, which sold the weapons, incluing the Bushmaster .223 rifle used in the shooting, to Nancy Lanza.
Seifert also declined to comment on any criminal investigation involving the shop, which was raided by the ATF after the Sandy Hook shooting.
The store continues to sell ammunition, clothes and other accessories.
In a statement in the days after the shooting, LaGuercia said he was "appalled" to the learn the guns had come from his shop.
“There is nothing more devastating than the loss of a child, and I am absolutely appalled that the product that was sold several years ago would be used in this type of crime,” he said. “Our hearts go out to the victims’ families and, as a father of three, I know firsthand of a parent’s loss and it’s the worst nightmare. We are cooperating with law enforcement in their efforts to get to the bottom of this senseless tragedy."