Lt. Gov. Gavin Newsom, running to replace Gov. Brown, has proposed a sweeping voter initiative that some call a declaration of war on law-abiding gun owners and Second Amendment rights.

Newsom, the former mayor of San Francisco while the city adopted tough ammo bans and mandatory gun lock laws that have seen extensive court challenges, has a five point list of gun control measures he wants to place in front of California voters in 2016.

These include an end to grandfathering of magazines capable of holding more than 10 rounds, relinquishment of weapons by those prohibited by the state from legal possession and mandatory reporting of lost or stolen guns. In addition, it would require background checks prior to all ammunition sales – a first for any state.

A staunch Democrat running for governor in 2018, Newsom is set to announce the proposition Thursday in San Francisco where he will be joined by co-authors of the measure, the Law Center to Prevent Gun Violence.

“In the last 72 hours – 68 people have been killed and 129 people have been injured due to gun violence in America,” Newsom posted to his social media accounts Wednesday without citation.

The ballot initiative, which would require 366,000 certified signatures to reach voters next November, proposes extensive changes to the state’s already tough gun laws, as reported by the Associated Press.

First, it would require point-of-sale background checks on ammunition purchases and require dealers to report lost or stolen rounds.

Next, it would revoke the grandfather status on detachable firearms magazines that were in the state prior to California’s adoption of a 2000 ban on what were termed large capacity magazines. Efforts to do the same in cities such as Los Angeles and Sunnyvale have met with both resistance and litigation.

Third, it would speed up the disarmament of those found by the state to be prohibited from firearms possession by making it a law that gun owners who lose their firearms rights turn in their guns within 14 days of their conviction. Currently, the state has a controversial Armed Prohibited Persons System that sends agents out looking for guns after cross-referencing criminal databases with lists of registered guns.

Finally, the initiative calls for the mandatory reporting of lost or stolen guns under penalty of law as well as increased reporting requirements by the state to the federal instant criminal background check system.

The proposal, still in its infancy, is already being blasted by gun rights advocates in the state, who are in the process of formulating a rapid response.

“We are already working with counsel to evaluate all possible options and ramping up an opposition campaign as we speak,” Firearms Policy Coalition President Brandon Combs told Guns.com by phone Wednesday. “If Gavin Newsom wants to declare war on law-abiding gun owners and Second Amendment rights, we’re certainly going to bring the fight to him.”

National pro-gun groups are questioning the real reason for Newsom, who was a vocal and early member of Michael Bloomberg’s Mayors Against Illegal Guns group.

“This proves just how extreme opponents of the Second Amendment really are,” Second Amendment Foundation Founder Alan Gottlieb told Guns.com in an email. “It also shows how frustrated the gun prohibition lobby is over not being able to enact most of their agenda. They are becoming unhinged.”

Gottlieb, who helped lead the fight against an ultimately successful anti-gun ballot measure in Washington state last year bankrolled in large part by a few wealthy donors, warned the same situation is popping up elsewhere.

“We in the gun rights movement must recognize that our constitutional rights are under assault by a handful of billionaires lead by Michael Bloomberg who can buy ballot measures at will. This is being orchestrated from Maine to California,” said Gottlieb.

Should the proposition make it to the ballot in a crucial election year that will see a new president, Combs cautioned the ultimate power will be in the hands of the voters.

“This is going to come down to votes,” Combs said. “Gun owners need to get moving on this now and be ready to show up in 2016.”