Missouri lawmakers expanded the potential for teachers to bring guns to schools, and for residents to openly carry firearms, in a vote on Thursday that capped a two-year effort by the Republican-led legislature to expand gun rights over the objections of the Democratic governor.

The new law will allow specially trained school employees to carry concealed guns on campuses under the designation of “school protection officers.” It will also allow anyone with a concealed weapons permit to carry guns openly — even in cities or towns that impose their own bans against open carrying. In addition, the minimum age to obtain a concealed weapons permit will drop to 19 from 21.

A more far-reaching measure that sought to nullify federal gun control laws had died in the final hours of the legislative session in May. Gov. Jay Nixon had last year vetoed a similar bill that could have subjected federal officers to state criminal charges and lawsuits for attempting to enforce federal gun control laws.

The new regulations, which this time garnered the two-thirds majority needed to override Nixon's veto, take effect in about a month.

Missouri school boards already have the power to allow employees with concealed gun permits to carry weapons on their campuses. The new law requires the state Department of Public Safety to establish training guidelines for schools wanting to designate a teacher or administrator as a "school protection officer" authorized to carry a concealed gun or self-defense spray.

"I think it's important that we train those individuals if they are going to be carrying," said state Sen. Will Kraus, R-Lee's Summit, who sponsored the bill.

The vote makes Missouri the 10th state to pass legislation allowing armed school employees since 20 children and six adults died during a mass shooting at Sandy Hook Elementary School in Newtown, Connecticut, in 2012.

States such as New York, California and Connecticut have ramped up gun restrictions since the shooting — a position backed by Democratic members of Missouri’s state Senate.

"The reality is we're making our cities less safe," said state Sen. Jolie Justus, D-Kansas City.

Underscoring those concerns, a Utah teacher suffered an accidental gunshot wound in an elementary school classroom, according to local news site KLS.com. School district spokesman Ben Horsley said the teacher, who had a concealed weapons permit, shot herself in either the foot or leg. He said that there were no students present when the shot was fired.

Al Jazeera and The Associated Press