One of America’s largest Second Amendment advocacy groups, the National Association for Gun Rights, is warning all gun owners against traveling to Massachusetts because of a proposed bill that it says would “ban more guns than any current law in the United States.”

“This is probably the biggest and worst package of gun control regulation I have ever seen, and that is saying a lot,” the president of the organization, Dudley Brown, said in a statement. “A ban on almost all guns, registration of every gun and magazine in the state — old and new — and a de facto ban on firearms carry are in the bill. Massachusetts just secured top position as the most hostile state in the union to gun owners.”

“Your gun rights and your freedom are at serious risk in the Commonwealth of Massachusetts,” Mr. Brown added. “If you live there you might want to pack your bags and if you are thinking of traveling there, you need to reconsider.”

The bill to which Mr. Brown is referring is House Docket 4420, which the legislators are calling An Act Modernizing Firearms Law. In total, the legislation already has 28 sponsors in the state house of representatives. 

The main target of the legislation is so-called ghost guns, which are firearms without serial numbers that are purchased online and assembled at home. Between 2018 and 2021, Massachusetts state police saw a 280 percent increase in the number of ghost guns seized on the streets. 

The bill also places a number of new restrictions on storing, purchasing, and carrying firearms. The age for purchasing semiautomatic shotguns and rifles would be raised to 21 from 18. All magazines, no matter the size, would be required to be labeled with serial numbers and registered with the state police. The bill would also update the definition of “firearm” to include non-lethal stun guns.

The sponsor of the bill, Representative Michael Day, says the purpose of the legislation is to fill “gaps” in the state’s licensing and criminal penalty laws. “The licensing laws that we have on the books work, right?” Mr. Day told the State House News Service following the introduction of the bill. “We’ve got the lowest rate of gun deaths in the continental U.S. of all gun deaths. The rate of gun deaths is still increasing, as they are nationwide, and Massachusetts isn’t immune to that.”

A number of legislative items related to firearm regulation have been introduced in Massachusetts this year. One state representative from the western part of the state, Mindy Domb, has made progress on a bill that would require state police to establish a voluntary buyback program for so-called assault weapons. 

The state attorney general, Andrea Campbell, is working with more than a dozen states to support a lawsuit brought by the government of Mexico against American gun manufacturers that would allow Mexico to sue for damages. 

The bill is a major priority for Democrats in the state. Mr. Day was assigned the task of reviewing gun laws already on the books in Massachusetts and proposing new restrictions to fill the so-called gaps. The state’s new governor, Maura Healey, who just hit the six-month mark in office, made restricting firearms ownership and usage a major part of her 2022 campaign. 

Ms. Healey, who previously served for eight years as the state attorney general, became one of Second Amendment advocates’ biggest villains in 2016 when she unilaterally grandfathered in certain semiautomatic rifles to be banned under the state’s assault weapons ban. She also tried to halt the manufacturing of all so-called assault weapons in the state. 

The National Association for Gun Rights is paying special attention to Massachusetts, given the state’s historically strict gun regulations. In June, it filed a lawsuit to end the state’s assault weapons ban, which was signed by Governor Romney in 2004. 

The proposed restrictions are borne of a landmark 2022 decision from the Supreme Court, New York State Pistol and Rifle Association, Inc. v. Bruen, which declared many blue state gun restrictions unconstitutional.