A leading gun group filed a lawsuit on Thursday in an effort to undue an expansion of Massachusetts’ assault weapons ban enacted unilaterally by the state’s attorney general.

The National Shooting Sports Foundation (NSSF), the largest trade association in the firearms industry, in conjunction with four Massachusetts gun dealers filed the suit against Attorney General Maura Healey (D.) in response to her attempt to redefine the state’s assault weapons ban.

Healey announced on July 20 that she was officially reinterpreting the language of the state’s decades-old ban. She said she would be vastly expanding what constitutes a so-called "copycat" of guns that are explicitly banned under the statute and accused the gun industry of skirting the law for years.

"The gun industry has openly defied our laws here in Massachusetts for nearly two decades," Healey said in her announcement. "That ends today. We have a moral and legal responsibility to ensure that combat-style weapons are off our streets and out of the hands of those who would use them to kill innocent people."

The NSSF said the changes are overly broad, vague, and unconstitutional.

"Attorney General Maura Healey’s actions were unconstitutional. Firearms retailers in Massachusetts cannot determine the meaning or scope of the Attorney General’s Enforcement Notice and subsequent explanations," Larry Keane, NSSF Senior Vice President, said in a statement on the suit. "Because criminal penalties can result due to Attorney General Healey’s unilateral reinterpretation of a state statute done without administrative process or input from affected parties, her office exceeded its lawful authority and retailers were deprived of their due process protections under the Fifth and Fourteenth Amendments."

"In addition, if the Attorney General’s Enforcement Notice is understood as applying to all semi-automatic firearms, it violates the Second and Fourteenth Amendments to keep and bear arms because it bans the manufacture, sale, and possession of a broad range of firearms in common use by the citizens of Massachusetts," Keane continued.

Keane said that the lawsuit was the only way to stop Healey’s actions.

"Unfortunately, Attorney General Healy’s unconstitutional action has left us no other option than to seek relief from the courts," he said.

The lawsuit comes on the heels of Healy’s aggressive and controversial use of a consumer protection law to go after gun companies, even one that does not sell guns in Massachusetts. Healy’s actions put her at the forefront of the gun control movement on the state level.

The NSSF is seeking declaratory relief and a permanent injunction to prevent enforcement of the attorney general’s changes.