SUMMER BALLENTINE | Associated Press

JEFFERSON CITY, Mo. (AP) — Missouri Republicans are clashing again with Democratic Gov. Jay Nixon on guns, as lawmakers approach a Wednesday vote that could overturn his veto of legislation allowing teachers to bring firearms to school and other residents to carry them openly in public.

After multiple setbacks, a veto override would mark a victory in Missouri for backers of expanded gun rights. A measure that would have voided federal gun control laws died in the final hours of session this May. Nixon vetoed a similar bill last year that could have subjected federal officers to state criminal charges and lawsuits for attempting to enforce federal gun control laws.

Lawmakers passed a less sweeping bill this session that would allow specially trained school employees to carry concealed guns on campuses. The measure also would allow anyone with a concealed weapons permit to carry their gun openly, even in cities or towns with bans against open carry.

The age to obtain a concealed weapons permit also would be lowered from 21 to 19 under the bill that was vetoed by Nixon.

Missouri lawmakers' efforts to pass gun legislation are part of a larger movement among conservative states.

After 20 children and six adults died in 2012 during a mass shooting at Sandy Hook Elementary School in Newtown, Connecticut, some Republican-led state legislatures, including Missouri's, fought against stricter gun control laws backed by Democratic President Barack Obama.

“I think that when you have a federal government that's trying to overreach and take our rights away and put restrictions on ammo and clips,” said state Sen. Will Kraus, R-Lee's Summit, “you motivate states to try to push back and say, `Hey, this is a constitutional right to bear arms.”'

Kraus said he believes lawmakers will be able to get the two-thirds vote needed in both chambers to override Nixon's veto, if enough Republicans show up for the vote.

David Kopel, an associate policy analyst for the libertarian think tank Cato Institute, said the president's policies played a powerful role in motivating Second Amendment activism.

About 30 states allow the open carrying of guns without a permit, and about 13 others require some sort of license.

Kansas in April approved a measure allowing the open carrying of firearms, which like Missouri will trump any local bans on open carry. Georgia gun owners can carry firearms openly in more places after the Legislature reduced open carry restrictions, and lawmakers voted to make Arkansas an open carry state last year.

Kopel said if passed, Missouri's proposal would set the state in the middle of the pack in terms of gun access.

Opponents argue the legislation still goes too far and takes power away from local government.

St. Louis first enacted a ban on open carry in the 1970s, said Eddie Roth, deputy chief of staff in the mayor's office. He said while that might work in rural areas, open carry “is a recipe for violence and injury and death” in urban settings.

Kansas City, Missouri, Mayor Sly James asked lawmakers to vote against the bill during a press conference Tuesday. The city banned open carry this July in response to the legislation.

“I want more of our urban neighborhoods to return to that type of vibrant, family-centered environment I grew up in, but to do that we need to make streets in our urban core as safe as the suburbs,” James said in a release. “Taking guns off the streets is key to that and Senate Bill 656 is a step in the wrong direction.”