Governor Newsom is proposing a 28th Amendment to the Constitution with the aim of addressing an issue that has divided Americans for decades — gun control.

“I’m proposing the 28th Amendment to the United States Constitution to help end our nation’s gun violence crisis,” Mr. Newsom said in a tweet. “The American people are sick of Congress’ inaction.”

The proposed amendment would raise the age to buy a firearm to 21, institute universal background checks nationwide, create “a reasonable waiting period for gun purchases,” and ban the civilian purpose of so-called assault weapons.

The amendment, Mr. Newsom said in a statement, would enshrine in the Constitution “common sense gun safety measures that Democrats, Republicans, Independents, and gun owners overwhelmingly support – while leaving the 2nd Amendment unchanged and respecting America’s gun-owning tradition.”

The Golden State governor framed his proposal as a response to his frustration over continuing gun violence and mass shootings. “I don’t know what the hell else to do,” he told Politico. “I don’t know what else is the answer.”

While Mr. Newsom made a point of saying that the four provisions of the amendment would leave the Second Amendment intact, gun rights advocates have rallied against his proposal.

A National Rifle Association spokeswoman, Amy Hunter, tells the Sun that Mr. Newsom’s proposal is a publicity stunt that “once again shows that his unhinged contempt for the right to self-defense has no bounds.”

“California is a beacon for violence because of Newsom’s embrace of policies that champion the criminal and penalize the law-abiding,” Ms. Hunter tells the Sun. “That is why the majority of Americans rightfully reject his California-style gun control.”  

Some members of Congress have thrown their support behind proposals similar to Mr. Newsom’s, like Congressman Mike Thompson, who has called on elected officials to “find the courage to act on the will of the American people.”

Mr. Thompson said that proposals like Mr. Newsom’s are broadly popular with the American people and cited an April Fox News poll as evidence. The survey found that 87 percent favor background checks for gun purchases, 81 percent back raising the age to 21 years old to purchase guns, and 77 percent favor a 30-day waiting period to purchase guns.

Among Mr. Newsom’s proposals, a ban on assault-style weapons and semi-automatic weapons was the least popular, according to the poll, which found it enjoyed the support of 61 percent of respondents.

One Second Amendment advocate and firearms policy scholar, John Lott, contends that despite the popularity of these proposals, the nationwide policy changes would not affect rates of gun violence.

“The main argument in favor of this point is that 18, 19, and 20-year-olds commit firearm-related crimes at relatively high rates, and that is true,” Mr. Lott tells the Sun. “But it is irrelevant to the ban that they are pushing.”

Mr. Lott says that “The issue isn’t whether that age group as a whole commit crimes but whether those who can legally buy a gun commit crimes,” adding that “Data shows that 18 to 20-year-olds who can pass background checks tend to be as law-abiding as older people.”

As of Thursday afternoon, top Republicans have not responded to Mr. Newsom’s proposal, potentially because the proposal has almost no chance of passing either the House, the Senate, or being ratified by a sufficient number of states.

Among advocates of more regulation of firearms, two of the leading organizations, Everytown for Gun Safety and Brady United Against Gun Violence, had not commented on the Newsom proposal by Thursday afternoon. Representatives for the groups did not immediately respond to requests for comment.

In order for an constitutional amendment to pass it must receive two-thirds support in the House and Senate and then be ratified by three-quarters, or 38, of the states. Alternatively, two-thirds of the state may convoke a so-called Article V convention, as Mr. Newsom proposes, to propose amendments to the states. After such a convention, three quarters of the states would be required to ratify and proposed amendments.

Although the proposal from Mr. Newsom faces long odds in passing, or even being brought to a vote, the move is in character for a governor who has staked his name in politics, partly, upon pushing gun control and is believed to have national political aspirations.

In response to Texas passing a law allowing people to sue abortion providers, Mr. Newsom supported a law allowing Californians to sue illegal gun distributors. Before then, Mr. Newsom had supported laws to restrict so-called “ghost guns,” which are difficult for law enforcement to trace; ban companies from marketing guns to children; and raising the age to purchase a firearm to 21 in California.

Republican state leaders have been moving in the opposite direction of Mr. Newsom, with 27 states now having “Constitutional Carry” or permitless carry laws. Some presidential hopefuls, like Governor DeSantis, have also recently thrown their weight behind policies like permitless carry in hopes of boosting their chances in the primaries.

On the national level, some House Republicans have rebelled against House leadership over a less prominent gun issue than what Mr. Newsom proposed.

Republicans like Representative Matt Gaetz have refused to vote on any other bill until House leadership brings a bill to the floor that would block a Bureau of Alcohol, Tobacco, Firearms and Explosives rule restricting pistol braces.

These devices, also known as stabilizing braces, are braces that attach the back of a gun to a forearm, serving a similar function to a bump stock. They are meant to allow for a shooter to stabilize the weapon or shoot one handed more easily.

The opposition to the pistol brace rule is bringing Republicans on the party’s right flank in conflict with leadership.