Mayor Bloomberg has made ridding the city of illegal guns one of his administration's major issues (it's also a big part of his potential national platform). Last year, he, on behalf of NYC, filed two federal lawsuits against out-of-state gun dealers, after sting operations revealed that the dealers were apparently selling guns illegally. While some dealers have settled, others are fighting back, countersuing the city.
The Bloomberg administration's sting operations involved two undercovers going to a dealer; one would ask all the questions, while the other "completely uninvolved in the sale process" would fill out the information for the gun purchase. Also known as a "straw purchase," the city says "federal law prohibits licensed dealers from selling firearms to individuals when they have a reasonable belief that the firearm being sold is not for the person who purports to be the purchaser."
Shortly after the Mayor's announcement of the stings, gun dealer Jay Wallace of Smyrna, Georgia, sued Mayor Bloomberg for defamatory comments. In a NY Times article, Wallace said of the Mayor's and others' comments (which included saying the dealers were "rogue," "the worst of the worst," and "bad apples"), "When someone comes along and says things that are pretty much totally opposite of the way that you are, and they really haven’t spoken to you, I really find offense with that.'
Wallace is represented by former Georgia congressman Bob Barr, and Georgia courts have said that Wallace's suit can proceed (Bloomberg's lawyers have appealed). Earlier this year, the Department of Justice said the gun dealers would not face criminal prosecution because the investigators in the stings may have acted illegally - one of the points in Wallace's suit. Some of Wallace's customers wonder why NYC didn't involve the feds, like the ATF, in the stings, and called the mayor's action a "witch hunt" and a ploy for political advancement. Barr's law partner told the Times that the lawsuit was against Bloomberg personally, because his actions were like "[sending] somebody down here to rob a bank...[he committed an] an extraterritorial act: like the British, he invaded us."
Bloomberg and Boston mayor Thomas Menino started Mayors Against Illegal Guns.