TRENTON, N.J. (CN) – Do-it-yourself gun kits, supposedly difficult to trace, weren’t able to slip past New Jersey’s top law enforcement officer.

“Ghost guns,” according to New Jersey Attorney General Gurbir Grewal, are partially assembled firearms that come in separate parts or in a kit, and sometimes even with instructions on how to put them together, like a child’s toy set.

(AP Photo/Marina Riker, File)

The founder and owner of California ghost gun company U.S. Patriot Armory, James Tromblee, Jr., is the defendant in a lawsuit Grewal filed Friday. He accuses Tromblee’s company of selling the assault firearms kit online to an undercover state investigator.

“New Jersey law is clear: ghost guns are illegal in our state,” Grewal said in a statement Friday. “Since U.S. Patriot Armory decided to ignore our laws and advertise and sell ghost guns to New Jersey residents, I’m taking action.”

In the complaint brought in Essex County Superior Court, Grewal’s office alleges Tromblee told customers the ghost guns were legal. But last November, Democratic New Jersey Governor Phil Murphy signed new laws against this type of gun, as well as 3-D printed guns and other “new-age” weapons.

Grewal says he has been papering ghost gun companies with cease-and-desist letters since last summer.

“The completed ‘ghost guns’ lack serial numbers, making it harder for law enforcement to trace the guns to their owners and solve gun-related crimes. ‘Ghost guns’ thus threaten both public safety and law enforcement safety,” the complaint states.

The lawsuit is the “first state civil enforcement action against a ghost gun company to demand penalties and get an order blocking New Jersey sales,” according to a statement from his office.

The four-count complaint charges U.S. Patriot Armory with violating the New Jersey Consumer Fraud Act and Hazardous Products Regulations.

“Is it legal?: YES!” the company allegedly claimed in advertisements for its products.

The lawsuit seeks court orders prohibiting the company from selling to New Jersey residents and demanding it provide a website disclaimer stating the products are illegal in the Garden State.

Earlier this week, Grewal announced the arrests of 12 people charged with trafficking ghost guns into New Jersey. Four of the men were charged with conspiring to sell six untraceable AR-15 assault rifles, according to his office.

At the end of this big week, he talked tough in his Friday statement.

“This is my message to the entire ghost gun industry: If you continue selling dangerous and unlawful weapons into our state, we will come after you in court, just like we did against U.S. Patriot Armory today,” the attorney general said.

A representative for U.S. Patriot Armory declined to comment Friday.