BOSTON (State House News Service) – Attorney General Maura Healey’s announcement Wednesday that she would step up enforcement of the state’s assault weapons ban, focusing on what she described as “copycat” guns, swiftly generated backlash from gun owners, dealers and activists who are viewing the move as an attack on their rights.

Protests outside the State House are planned for Thursday and Saturday, with organizers describing Healey’s actions as unconstitutional. Less than 24 hours after her announcement, more than 15,000 people had signed an online petition calling on Gov. Charlie Baker to overturn Healey’s decision and nearly 500 had joined a Facebook group calling for her to be recalled or impeached.

“I’ve been looking at the reactions that’s been going on in social media and text messages I’ve been getting, and I think that Maura Healey really stepped in it,” Massachusetts Gun Rights President Christopher Pinto told the News Service. “This is like the day of infamy for Maura Healey. She’s going to awaken the sleeping giant of gun owners in Massachusetts. There’s nearly half a million of us in Massachusetts – Republican, Democrat and Independent — and she’s really woken up a sleeping giant, and her chances of getting elected governor or keeping her office could be over.”

Healey held a press conference Wednesday to announce her office would enhance enforcement of the state’s 1998 assault weapon ban and had issued a notice to the state’s 350 gun sellers advising them that copies or duplicates of banned guns were also illegal in Massachusetts.

“Increasingly, as we have seen, assault weapons are the weapons of choice for mass shooters,” Healey said. “They’re the kinds of weapons used in Orlando, San Bernardino, Aurora, Colorado, and Newtown, the kind of weapon used this past weekend to brutally target and kill three Baton Rouge police officers.”

The announcement created a rush on some Massachusetts gun stores, as consumers looked to buy items they worried would soon be prohibited.

Pullman Arms in Worcester stayed open until midnight, encouraging customers in social media posts to arrive by 10:30 p.m. to fill out necessary paperwork. Templeton’s Minuteman Armory got supply shipments from New Hampshire gun shops to keep up with demand Wednesday, and planned to open later than usual on Thursday after staff remained at the store until 1:30 a.m.

“My wife has always wanted her own AR-15 since she shot her brother’s. I went out and bought her one,” Pinto said. “My wife should probably send Maura Healey a thank-you note.”

Pinto described AR-15 as “the most common rifle out there,” comparing it to “the iPhone 6 of the shooting world.”

Noting that the 2016 platform adopted this week at the Republican National Convention includes language opposing laws that would “ban the sale of the most popular and common modern rifle,” Pinto said he believed the timing of Healey’s announcement was politically motivated.

Jim Wallace, the executive director of the Gun Owners Action League of Massachusetts, said he also views Healey’s actions as a “political stunt.”

“These laws were passed in 1998, they were redone in 2004, then they were reviewed in 2014, so the Legislature is already fine with what is going on,” Wallace said Wednesday. “What other reason would a person unilaterally decide, I’m going to change the rules overnight?”

Speakers at Healey’s press conference Wednesday said her actions did not represent a new law or set of regulations but heightened enforcement of an existing statute.

Gun rights activists and firearm retailers have been encouraging others opposing the move to reach out to the governor and lawmakers.

“Governor Baker supports the Commonwealth’s assault weapons ban, believes our comprehensive state gun laws work well in protecting the people of Massachusetts, and believes that the Attorney General has the authority to enforce the law to crack down on the sale of guns that skirt the assault weapons ban,” Baker press secretary Billy Pitman said.

During an appearance on WGBH Radio Thursday, Baker said Healey has the “authority and the jurisdiction” to notify gun dealers that weapons meeting certain criteria would qualify as banned assault weapons and that he hopes a list of banned guns will be produced so people can have clarity.

“If people are in fact selling weapons that violate the Massachusetts assault weapon ban, then that should be dealt with and people should do something about it,” he said. “I think the big issue, especially in the short term, is going to be the confusion around which weapons this applies to and which weapons it doesn’t apply to.”

Healey’s enforcement notice said that forbidden copycat guns are those that are “substantially similar in construction and configuration” to banned weapons or have interchangeable key parts. She said she would not enforce the ban against gun owners who bought or sold such weapons before Wednesday.

The attorney general’s announcement was lauded Wednesday by U.S. Reps. Katherine Clark, Seth Moulton, and Joe Kennedy, Boston Police Commissioner William Evans, district attorneys Daniel Conley of Suffolk County and Marian Ryan of Middlesex County, other members of law enforcement and anti-violence advocates.

Healey said gun manufacturers “have taken it upon themselves to interpret the law as they see fit, and to make tweaks in an effort to evade application of our state assault weapons ban.” She described the actions by her office as a clarification that will “give us the full protections of the state’s assault weapons ban to do what it was intended to do.”

With both the House and Senate meeting in formal sessions on Saturday, GOAL is planning a 10 a.m. rally on the State House steps. The event will follow a separate demonstration scheduled for 5 p.m. Thursday, which organizers describe as a “protest against the unconstitutional assault weapons ruling by MA Attorney General Maura Healey.”

“It’s going to be peaceful,” said Joseph Locke, a board member of the Bridgewater State University College Republicans and an organizer of Thursday’s protest. “There will not be people open-carrying, nobody will be making a scene or trying to make some sort of over the top political statement.”

Locke said he viewed Healey’s enforcement announcement as “utterly disregarding the due process of the law,” and said it caught many off-guard.

“There has been talk of potentially a class action lawsuit against the attorney general, but nothing has been set in stone as we try to figure out what the appropriate response is,” he said.

A day after Healey’s announcement, opponents of the measure said they believe action needs to be taken but they are still working to interpret the ramifications of the enforcement and the best response.

“We’re trying to determine the best course of action from here and what that is is yet to be determined, whether it be legislative or judicial action,” said Rep. Marc Lombardo, a Billerica Republican. “But it is clear that something needs to happen to take on this assault to law-abiding citizens of the commonwealth.”

Through aides, Healey declined comment on the opposition efforts that have gained momentum since she announced her crackdown on Wednesday.