Yet even if the White House and Republicans agree that Guard troops should be sent to the border, there's little consensus on what exactly they'd be empowered to do.
There's precedent for such a move. In 2006, the Bush administration mobilized the Guard to help with security efforts while 6,000 new Border Patrol agents were brought online. Former Bush officials say the troops played a valuable role during their two-year deployment.
"Clearly if they are properly deployed as part of a strategy, they can be very helpful," said Jayson Ahern, who served as deputy and then acting commissioner of U.S. Customs and Border Protection from 2007 to 2009. "What's not helpful is uncoordinated deployments that don't have a good plan and that aren't well thought-out."
The key in that case, Ahern said, was that it was the federal government, through the Department of Homeland Security and the Pentagon, mobilizing the Guard, not individual states. The troops were "properly planned, sanctioned, and under supervision and the direction of the Border Patrol," he said. "From a training standpoint, there's very strict limitations on what the Guard can and cannot do, particularly around people."
Guard troops can't step in the shoes of federal officers to enforce immigration policy, they can't conduct law-enforcement activities, and only in rare cases can they make arrests. "If they, solely, stopped and detained someone, I think that would be a stretch of their authority," Ahern said.
Perry's office seems to get that. Travis Considine, a Perry spokesman, said the Texas troops aren't being sent to deal with the child-migrant crisis at all, but to help combat "crime and cartel activity that is resulting from our unsecured border." The Guard, he said, "will be working side-by-side with law enforcement, who can detain individuals and refer them to the appropriate federal authorities."
"Criminals," he added, "are taking advantage of the fact that the Border Patrol is being diverted from the law-enforcement duties to help with humanitarian aid."
The Texas Guard will remain under Perry's direction in what appears to be the kind of the uncoordinated response that Ahern says should be avoided. At the same time, Obama's team, comprised of officials from DHS and the Defense Department, will determine whether the administration needs to mobilize the Guard. And if it does, the troops are expected to serve much of the same role they served in 2006-07, backing up the Border Patrol and performing administrative tasks.
Deploying the Guard to "assist with the humanitarian care and needs" of children traveling without a parent is a component of a House Republican working group's recommendations to address the crisis.
Led by Rep. Kay Granger of Texas, the working group doesn't have an estimate on the number of troops it would deploy. It'd be a short-term assignment, Rep. Mario Diaz-Balart of Florida said Thursday, to relieve a "stretched-thin" Border Patrol.