RICHMOND, Va.  A gun-rights organization is planning to hold a "gun giveaway" this week inside a Fairfax County, Va., government building to protest Mayor Bloomberg's efforts to crack down on illegal gun sales in Virginia.

On Thursday at the Mason District Government Center in Annandale, the Virginia Citizens Defense League will hold a drawing for a semiautomatic pistol, a hunting rifle, and ammunition to raise money for two gun shops that Bloomberg has filed suit against.

And because it's Virginia, many people at the "Bloomberg Gun Giveaway" will probably be armed. League members routinely lobby the Virginia General Assembly with guns on their hips.

Fairfax County officials are furious about a gun event staged in a government building but say they can't do much to stop it because the General Assembly won't allow local governments to ban the possession of guns in public buildings.

"These people have concealed-weapons permits, and we know they are packing, but they are legal," said Fairfax Supervisor Penelope Gross, a Democrat of Mason. "I swore to uphold the law, whether I like it or don't, and I don't."

Under Virginia law, a person 21 or older can obtain a permit for carrying a concealed handgun. No permit is needed if someone 18 or older wants to carry a gun in plain sight. The league, which says it has 3,300 members, sent out an e-mail this past week reminding members that "lawful gun carry is optional at the Bloomberg Gun Giveaway."

The Citizens Defense League is trying to raise money for Bob Moates Sport Shop in Richmond and Old Dominion Gun and Tackle in Danville, two of the six Virginia dealers New York has sued. The legal challenges stem from Bloomberg's effort to prove that Virginia is a major contributor to violent crime in New York.

Convinced that Virginia gun dealers are selling weapons illegally, Mr. Bloomberg sent undercover agents to the stores to conduct "straw purchases," in which one person fills out a form and buys a gun for someone else. According to a lawsuit filed a year ago in federal court in Brooklyn, the city alleges that Bob Moates and Old Dominion Gun illegally sold guns to Mr. Bloomberg's agents.

Philip Van Cleave, president of the Virginia Citizens Defense League, said, "We are trying to protect the gun stores that Bloomberg attacked." He called the Republican mayor "a vigilante. He has come into Virginia and taken the law into his own hands."

Bloomberg spokesman Jason Post responded: "We will not for one second back away from our tough law enforcement efforts against illegal guns, which have made New York the safest big city in the country. We caught gun dealers on videotape flagrantly violating the law."

To help pay the gun dealers' legal fees, the defense league has encouraged people to buy weapons from the Moates and Old Dominion stores. Those who spend more than $100 will have their names entered into Thursday's drawing. Winners will be able to view the guns at the meeting but will take possession of their weapon at a gun shop after filling out the paperwork, Mr. Van Cleave said.

When she learned of the event last week, Ms. Gross intervened to see whether the drawing was legal. Ms. Gross concluded that the county cannot prohibit a group from using community meeting rooms because of its political views. And because the organizers won't be selling tickets at the meeting, Ms. Gross said it appears that the group is not violating state or local laws regulating raffles.

Even so, Del. Adam Ebbin, a Democrat who represents parts of Alexandria and Fairfax County, called the event "embarrassing."

"I guess this group wants to rub salt in the wound and prove we can't stop firearms in our buildings," Mr. Ebbin said. "It would be nice if they put their energy into making sure people who shouldn't have guns don't, instead of passing around extra guns."

The gun giveaway is turning off some sportsmen groups. "It really gives legitimate gun owners and shooters a bad name when you see something like this," said Fairfax resident Bob Ricker, executive director of the American Hunters and Shooters Association.

Fairfax has been pushing for state legislation that would allow local governments to ban the possession of firearms in county buildings, police stations and public libraries. The Republican-controlled General Assembly has killed the bills, demonstrating the disconnect between Northern Virginia and the rest of the state on gun-control issues.

Del. C.L. "Clay" Athey Jr., a Republican of Warren, said law-abiding citizens who carry guns shouldn't have restrictions placed on where they can go.

"The reality is, it may be helpful for someone who is qualified to carry a concealed weapon to be there in a public building in case some [shooting] occurs," said Mr. Athey, noting that many retired police officers have concealed-weapons permits.

The Virginia Citizens Defense League was formed in 1994 to fight for the rights of people who want to carry concealed weapons.