>> President Trump calls out the National Guard to patrol the US border. The big question what are they gonna do when they get there? I'm Andy Sullivan in Washington where Trump is moving quickly to post troops along the border as a caravan of migrants heads north through Mexico.
It's a move that's likely to please his conservative supports even though some of them are livid that he hasn't been able to shake loose enough funding for his promised border wall. So the symbolism is good, but it's not clear whether these troops will be able to do much once they actually get in the field.
>> The threat is real.>> Pointing to a recent spike in illegal border crossings, US Homeland Security Chief Kirstjen Nielsen offered the first details on the coming troop deployment from the White House briefing room.>> It will be strong. It will be as many as is needed to fill the gaps that we have today.
>> The move comes amid heavy media coverage of a group of some 1,200 Central American migrants, who Trump has said will be trying to enter the United States. Border crossings are down sharply from their peak during the Obama years, but Nielsen said an upswing in attempted crossings has prompted Trump to act now.
>> The numbers continue to increase. April traditionally is a month in which we see more folks crossing the border without a legal right to do so.>> Calling in the troops is an idea that Trump's two predecessors Barack Obama and George W Bush both tried in their day.
Like them, Trump will be running up against tough US laws that sharply limit the ability of soldiers to enforce domestic laws. When Bush deployed troops a decade ago, they were not permitted to arrest anyone. They ended up repairing fences and monitoring surveillance video. On top of that, the governor of each border state has to sign off.
That could be a tough sell in Democrat controlled California.>> When you have thousands of people that decide to just walk into our country and we don't have any laws that can protect it.>> Most of Trumps immigration headaches can only be fixed by Congress. One example, the policy known as catch and release.
That allows some immigrants to go free until their day in court.>> We have to change our policies fast.>> Politically this move lets Trump show that he's trying to get a handle on the problem even though his border wall remains unbuilt. But the reality is Trump will need Congress to enact the kinds of changes that he has in mind and with mid-term elections fast approaching, lawmakers have shown little appetite to take on this explosive issue.