Gov. Gavin Newsom proposed Thursday an amendment to the U.S. Constitution that would dramatically roll back gun rights enshrined in the Second Amendment since the nation’s founding.

“The American people are sick of Congress’ inaction,” Newsom said through his personal Twitter account.

His proposed 28th Amendment to the constitution, he said in a tweet that included a video of him dressed in a blue suit and tie describing his proposal, would enshrine four “widely supported gun safety freedoms — while leaving the 2nd Amendment intact.”

His proposal calls for raising the minimum age to purchase any gun to 21, universal background checks on all gun transfers, a “reasonable” waiting period for gun buyers to pick up their weapon and banning the civilian purchase of “assault weapons.” He added in the video that the proposal “will guarantee states, as well, the ability to enact common-sense gun safety laws.”

Gun-rights supporters called it a political gimmick by a politician with national ambitions that if adopted would roll back people’s rights to defend themselves.

“Newsom’s latest publicly stunt once again shows that his unhinged contempt for the right to self-defense has no bounds,” the National Rifle Association said in a response Thursday. “California is a beacon for violence because of Newsom’s embrace of policies that champion the criminal and penalize the law-abiding. That is why the majority of Americans rightfully reject his California-style gun control.”

But advocates for more restrictions on guns cheered Newsom’s proposal.

“These are commonsense solutions that the vast majority of Americans support and it’s past time to make them the law of the land,” Moms Demand Action founder Shannon Watts said in a Twitter response to Newsom’s announcement.

The nation’s founders didn’t make it easy to amend the U.S. Constitution. The Constitution provides that an amendment may be proposed either by the Congress with a two-thirds majority vote in both the House of Representatives and the Senate, or by a constitutional convention called for by two-thirds of the state legislatures, according to the Office of the Federal Register. None of the 27 amendments to the Constitution have been proposed by constitutional convention.

A proposed amendment becomes part of the Constitution as soon as it is ratified by three-fourths of the states — 38 out of 50. The Constitution’s last amendment, ratified in 1992, requires an election before raises that U.S. senators and representatives approve for themselves can take effect.

Larry Gerston, San Jose State University political science professor emeritus, said it would be quite difficult to persuade enough lawmakers and senators in rural states where hunting and gun rights are popular to go along with a proposal that would be assailed as an assault on their culture and constitutional rights.

“We’ve got a gun culture in many of these states and they view this as an intrusion,” Gerston said. “There have been more than 11,000 attempts to amend the Constitution since 1789. Twenty-seven have succeeded and 10 of those are the Bill of Bights.”

But Gerson added that the long-shot proposal gives Newsom another opportunity to raise his national profile ahead of an assumed future presidential campaign. Though Newsom has said he supports and won’t challenge the re-election of President Joe Biden, a fellow Democrat, he often is mentioned as one of the party’s top prospects for the White House, given his landslide victories in the nation’s most populous state.

“It’s just one more opportunity for Newsom to get on the national stage on a controversial issue,” Gerston said. “He’s already been out there on immigration, abortion — California is a sanctuary state for both of those. These are all big social issues. This is one more issue where he’s come out there and laid his cards on table. He’s developing this portfolio where once he presents himself as a national candidate, it’s just one more step for him to be in position should interest in the presidency ever develop.”

Parts of Newsom’s proposed amendment already are law across much of the country.

Federal law prohibits licensed firearms dealers from selling a handgun to anyone under age 21. California and nine other states also prohibit rifle and shotgun sales to those under age 21, according to the Giffords Law Center. Several states also prohibit possession of a gun by those under 21.

Federal law requires background checks on firearm sales by federally licensed dealers, but California and 20 other states also extend that requirement to at least some gun sales or transfers by unlicensed private sellers, Giffords says.

The only waiting period on gun purchases under federal law is the time it takes licensed dealers to conduct a background check. But California and nine other states impose waiting periods on at least some gun sales — 10 days in the Golden State, Giffords says.

Congress banned sales of “assault weapons” and large-capacity ammunition magazines from 1994 to 2004, when lawmakers allowed it to expire amid dispute over its effectiveness, but California and nine other states maintain similar bans, Giffords says.

A national Monmouth University poll in April found varied support for gun rights, with 51% saying the right to bear arms is important but should have restrictions and 81% supporting universal background checks. But just 46% support banning assault weapons, with 49% opposed.

Critics argue the “assault weapons” favored by rampage shooters for shock value — semi-automatic rifles with military-style features such as pistol grips that fire one bullet per trigger pull — are functionally no different than rifles and pistols commonly sold to hunters and target shooters. The weapons carried by soldiers can fire continuously at a higher rate with one trigger pull, and largely are off-limits to civilians.

Eugene Volokh, who teaches constitutional law at the University of California-Los Angeles, said restrictions on assault weapons and the legal age to buy guns are “quite substantial.”