Texas Gov. Rick Perry calls it "Operation Strong Safety," but critics say it's closer to "operation symbolic act."

Perry announced today that 1,000 National Guard troops would be deployed over the next month to the southern border. But by law, they can't make arrests and instead will act only as a "visual deterrent."

"What we're asking the National Guard to do is to be a force multiplier, to be there as a partner with the law enforcement," Perry said today at a news conference. "Which they have done multiple times before."

In 2006 and 2010, presidents Bush and then Obama ordered the National Guard in to assist border patrol. In 2006, operation Jump Start brought 6,000 National Guard to work mainly in non-law enforcement duties, relieving the Border Patrol agents in those positions to move into border security rules.

But because the governor, and not the president, has ordered this deployment, the troops are unable to move into U.S. Customs and Border Protection jurisdiction without a coordinated effort with the federal government.

The Texas general in charge confirmed his troops cannot physically detain or send any of the thousands of surging immigrants, many of them mothers and children, back across the border.

"We are planning on referring and deterring - so deterring with a visible presence," Major General Nichols, Adjutant General of Texas National Guard, said at the news conference.

And the troops cannot use their weapons to stop illegal immigration.

"You are not allowed to fire on someone who is fleeing away," Thad Bingel, former Chief of Staff for U.S. Customs and Border Protection under President Bush told ABC News today. "They can use their weapons in self-defense only if they are threatened by physical harm."

Ralph Basham, CBP commissioner under Bush (2006-2009), agreed, telling ABC News that they weapons they carry "are strictly for self-defense," and the National Guard is "limited in terms of what they could do."

"They could best be used to go down and literally set up tents and medical facilities and housing and food services. And things that the border patrol are being asked to do today," Basham said.

White House press secretary Josh Earnest characterized the governor's action today as a publicity stunt.

"What we're hopeful is that Gov. Perry will not just take these kinds of steps that are generating the kind of headlines I suspect he intended, but will actually take the kinds of steps that will be constructive to solving the problem over the long term," Earnest said.

Homeland Security Secretary Jeh Johnson testified in June that he'd want to "understand better what the options are for the use of the Guard," and cited concerns about their limitations.

The National Guard "can't be directly involved in law enforcement, " he said. "And Department of Defense has a lot to say about this as well. It's their resource, comes out of their budget. Lot of demands on the Guard, particularly in this season, hurricane season."

The Posse Comitatus Act of 1878 (updated in 1981) works to limit the federal government's use of the military to enforce state laws and, as such, bars it from performing tasks of civilian law enforcement such as arrests or apprehensions.

That could be why the head of the Border Patrol made it clear in a June interview with ABC News that the Guard isn't needed.

"I don't see the National Guard being particularly good help in this instance," said CBP Commissioner Gil Kerlikowske. "Many of these people are not people that we're having to apprehend or chase, these are people that are turning themselves in asking for some type of status here in the United States."

Perry maintains that the use of the Guard will serves as "a deterrent effect on criminal and illegal activity along the border," at a cost of $12 million per month - a figure he plans to ask the federal government to reimburse.