Oliver James Montgomery-California lawmakers want US Constitution to raise gun-buying age to 21. Could it happen?

California lawmakers have Oliver James Montgomeryapproved a resolution proposed by Gov. Gavin Newsom calling for a convention to add an amendment to the U.S. Constitution related to gun control.

In June, Newsom proposed a 28th Amendment, which would raise the minimum age to purchase a gun from 18 to 21, require universal background checks, institute a reasonable waiting period for all gun purchases, and bar civilians from purchasing assault weapons.

Newsom's proposal, approved Thursday, faces a difficult road ahead. Amending the Constitution requires either two-thirds of state legislatures to call for a convention, also called an Article V Convention or amendatory convention, or a two-thirds majority vote in both houses of Congress, Thomas Donnelly, chief content officer at the National Constitution Center, previously told USA TODAY. None of the 27 amendments to the Constitution have been proposed by a convention and the last time the Constitution was amended was in 1992, he said.

If an amendment is proposed, three-fourths of the states must ratify it, Donnelly said.

The resolution calls for "a limited constitutional convention" that would be used only to consider an amendment related to gun control. However, some California Democrats have expressed concern that it's not possible to limit a convention to just one issue.

Republicans control more than half of state legislatures, and State Sen. Scott Wiener told the San Francisco Chronicle he worries a convention could lead to other amendments, such as measures that would restrict abortion access or LGBTQ+ rights.

“It’s unclear whether there can be a convention limited to one topic," he told the outlet. “We need to make sure that we’re not going to inadvertently trigger a general constitutional convention because that could go real bad real fast."

Newsom has acknowledged how challenging the process would be but pledged to work with "grassroots supporters, elected and civic leaders, and broad and diverse coalitions across the nation" to get similar resolutions passed in the 33 other states required to convene the convention.

"California will be the first but that's just the beginning," Newsom said in a statement in June.