Dec. 18, 2012 -- Michigan Gov. Rick Snyder today vetoed a bill that would have invalidated "gun free" zones like those at schools and churches.

The law was passed by the state legislature in Michigan the day before the Newtown, Conn., elementary school shooting. It would have allowed individual schools to ban guns on their property, but Snyder vetoed it because of concerns that public schools did not retain enough power to keep guns off their campuses.

"While we must vigilantly protect the rights of law-abiding firearm owners, we also must ensure the right of designated public entities to exercise their best discretion in matters of safety and security," he said. "These public venues need clear legal authority to ban firearms on their premises if they see fit to do so."

But some state laws already permit individual school districts to allow concealed weapons on campus. The thinking is that law-abiding citizens with concealed weapons can deter and react to the person bent on destruction.

Four days after the deadly school shooting in Connecticut that left 20 children and six teachers dead, two Republican governors have spoken favorably of considering proposals to put guns in the hands of teachers and administrators.

Texas Gov. Rick Perry expressed support for allowing school districts to determine whether teachers can carry concealed handguns in class, which at least one Texas district already permits.

"In the state of Texas, if you go through the process, have been trained, and you are a handgun-licensed individual, you should be able to carry a gun anywhere in the state," Perry told the NE Tarrant County Tea Party Monday evening, according to ABC News affiliate WFAA-TV in Dallas-Fort Worth.

Virginia Gov. McDonnell said during a WTOP radio program today, "I know there's been a knee-jerk reaction against that. I think there should at least be a discussion of that. If people were armed, not just a police officer but other school officials who were trained and chose to have a weapon, certainly there would have been an opportunity to stop aggressors coming into the schools. So I think that's a reasonable discussion that ought to be had."

This is not the majority opinion in the United States, however. An ABC News-Washington Post poll conducted in the aftermath of the Friday shooting found that 54 percent of Americans favor stricter gun control laws in general and 59 percent support a ban specifically on high-capacity ammunition clips such as the ones used in Newtown.

But Perry and McDonnell are far from alone.

One Texas school district, the Harrold Independent School District, adopted a policy in 2007 allowing teachers to carry concealed handguns in schools. Almost 200 miles northwest of Dallas, Harrold is a small school district near the Texas-Oklahoma border that teaches 100 children K-12.

"We're a rural community," Harrold superintendent David Thweatt told ABC News in a phone interview. "We're in a county about a little smaller than the state of Rhode of island, so we're 30 minutes from law enforcement. Thirty minutes is an extremely long length of time."

Harrold implemented the "Guardian Plan," the district's policy that allows teachers to carry concealed handguns, after the 2006 shooting at an Amish school in Nickel Mines, Pa., which killed five young girls, and the 2007 massacre at Virginia Tech that led to the death of 32 students and teachers.

"We were just concerned with trying to protect our kids, and there were enough shootings, as far as I was concerned, to develop this plan," Thweatt said.

Click Here: Complete Coverage of Sandy Hook Massacre

In Perry's state of Texas, lawmakers in 2011 narrowly failed to pass legislation allowing permitted handgun owners to carry concealed guns on college campuses. But they are allowed in the statehouse.

Five states have provisions allowing concealed weapons on college campuses and 23 others allow individual schools to allow guns on college campuses.

Some proponents wouldn't stop at college campuses.

Rep. Louie Gohmert, R-Texas, a gun rights advocate who represents an east Texas district, said he wished that the principal at Sandy Hook Elementary School had been armed when Adam Lanza opened fire on the young school children and teachers Friday morning.

"I wish to God she had had an M-4 in her office, locked up so when she heard gunfire, she pulls it out and she didn't have to lunge heroically with nothing in her hands. But she takes him out, takes his head off before he can kill those precious kids," Gohmert said on FOX News Sunday.

In Texas' Harrold Independent School District, The Guardian Plan consists of four components. An employee must obtain a concealed handgun license from the state of Texas, and the school board would approve them individually to carry in schools. The teachers must then go through extended training, and the ammunition used in the guns must be frangible, meaning it is made of small particles and breaks apart when it hits a hard object like wood or a plastic wall.

Harrold employs about 25 teachers and personnel, but superintendent Thweatt would not specify how many employees or which ones carry concealed weapons in the schools. Thweatt said many parents in his district support the concealed-handgun policy for teachers.

"Parents often cite that the reason they're bringing their kids to our schools is because we have better security for them," he said. "When you send your kids to school, you want them to come home to you."

In the wake of the massacre at Sandy Hook Elementary, Thweatt says more school districts in Texas have reached out to him for information about Harrold's concealed-handgun policy.

The Texas penal code prohibits weapons from being used in schools or educational institutions "unless, pursuant to written regulations or written authorization of the institution," language allows for school boards to determine whether teachers can carry handguns in schools.

Debbie Ratcliffe, a spokeswoman for the Texas Education Agency, said the agency has not heard of other school districts' wishing to implement the same policy as Harrold but noted that the districts would not be required to report it to the agency.