New York state is cracking down on made-to-assemble guns sold over the Internet. (Photo: NYAG)

More than a dozen websites operators who sell ready-to-assemble assault rifles and other guns over the Internet have been ordered to stop doing business in New York State, under a sweeping “cease and desist” order issued by New York Attorney General Letitia James.

The possession, manufacture and sale of assault weapons is illegal in New York, but the companies are able to exploiting a loophole in the legal definition of a firearm, according to the AG’s office.

A lower piece of a gun, known as the receiver, is the only sub-assembly that legally constitutes a firearm under federal law. It’s responsible for the actual “firing” of the bullet.

This unassembled AR-15 assault rifle is being sold over the Internet.

If the receiver is sold incomplete — lacking certain holes, slots, or cavities — it falls outside the legal definition.

Internet operators can legally sell a weapon as long as the receiver is unfinished. Often, it’s only a matter of drilling a few holes to make it fully functional.

Because the weapon is sold privately and in pieces, it’s unregistered and contains no serial numbers, making it difficult, if not impossible to trace. “If they don’t know you have it, they can’t take it,” is the motto of one company.

“There is only one purpose for the products that these companies are selling — to manufacture illegal and deadly assault weapons,” said James.

“The proliferation of these types of weapons has not only caused indescribable suffering across the country, but gravely endanger every New Yorker. We must make sure that these illegal and untraceable guns are not built in New York,” the order says. (Read the letter here)

The companies have been marketing receivers as “80 percent” complete to evade federal regulations.

The weapons are called “ghost guns” because they are virtually untraceable.

Buyers don’t have a federal firearms license or submit to a background check. Many of these sellers also sell specialized jigs — or stencil-like precision tools–to make the receiver functional.

Anyone caught with a ghost gun faces penalties of up to $5,000 for each violation and forfeiture of the gun.

Ghost guns have been an on-going problem. In September 2015, the New York AG’s office conducted “Operation Ghostbuster,” an investigation that led to a 32-count indictment against two ghost gun sellers, Thomas Weber and Antonio Himonitis in Nassau and Suffolk counties.

Himonitis and a co-conspirator ordered unfinished gun parts from different manufacturers across the country and assembled them into at least a dozen fully-functional ghost guns, which they then sold to undercover investigators posing as gun trafficking gang members.

Himonitis and Weber were in prison at the time they first devised a plan to assemble and sell the illegal weapons. It was the first such case in New York.

“Ghost guns represent a new, dangerous frontier of illegal firearm trafficking—the creation of homemade, completely untraceable, military-grade firearms,” said then Attorney General Eric Schneiderman.

“It does not matter if you build it yourself or buy it off the street corner—an illegal gun is an illegal gun, and we will prosecute you to the fullest extent of the law.”

A “stripped” AR-15 receiver sells for as little as $60 over the Internet, according to a cursory search.

An unassembled AR-15 assault rifle sells for as little as $339. In contrast, a fully assembled model purchased at a gun store can sell for up to $1,000.