GEOFF BENNETT: Today, a federal judge in California heard the state's challenge to President Trump's deployment of the National Guard and U.S. Marines to Los Angeles to assist with enforcing federal immigration laws.

AMNA NAWAZ: The administration argues that the president had discretion to deploy the troops and they're in the city to protect law enforcement.

Meanwhile, California Governor Gavin Newsom, who filed the temporary restraining order earlier this week, has said the White House's actions are a -- quote -- "power grab" that violates the U.S. Constitution.

Joining me now to discuss this further is Liza Goitein.

She's senior director at the Brennan Center for Justice's Liberty and National Security Program.

Liza, welcome back to the program and thanks for joining us.

Let's start with this legal fight now over the federal deployment of troops in response to those protests against immigration raids.

Walk us through the administration's legal main argument here.

How are they justifying the deployment of those troops?

ELIZABETH GOITEIN, Brennan Center for Justice: So, the administration is relying on an obscure statute that has actually never before been used as a stand-alone authority to quell civil unrest.

That's a law that requires, in order to quell civil unrest, that there be a rebellion against government authority or that it be impossible for the president to execute the law without deploying the military.

Now, those conditions don't really seem to have been met here, but what the government is arguing is that the court cannot review whether the president's findings were correct or not, that as long as the president says that there was a rebellion, there was a rebellion.

So that's really the main argument.

The government is also claiming a vast inherent constitutional authority to deploy federal troops to protect federal property and functions.

This is a longstanding executive branch theory, but it really hasn't been tested in the courts yet.

AMNA NAWAZ: And, in challenging that federal deployment of troops, we saw in Governor Newsom's lawsuit the claim that the administration didn't have the authority to federalize the National Guard without the state's consent.

He claims they violated the 10th Amendment.

And they also argued that this kind of civil unrest that they're seeing can be handled and contained by state and local authorities.

What do you make of that argument?

ELIZABETH GOITEIN: Well, quelling civil unrest is a responsibility that is entrusted to state and local law enforcement, state and local officers under the Constitution, except in the most extreme circumstances.

And the Department of Justice has historically taken the position that federal troops should be deployed for this purpose only if the state requests assistance, if there is outright defiance of a federal court order, or if state and local law enforcement are completely overwhelmed.

And, once again, none of these conditions are present here.

The last time that a president federalized the National Guard and deployed them to a state to quell civil unrest over the objection of a governor was in 1965, during the civil rights era, to protect civil rights marchers who are marching from Montgomery to Selma, Alabama.

So that has happened really in the in circumstances where state and local law enforcement were not willing to take action against threats of violence or violence against civil rights marchers, African Americans who were trying to attend school, or in cases where state and local law enforcement were in open defiance of court orders.

AMNA NAWAZ: Liza, one important distinction I want to get your take on here.

We have heard that the National Guard is saying the officers have been accompanying ICE on immigration raids, that the federal officers there are not enforcing arrests yet there.

What would have to happen legally for those troops to act in that way?

ELIZABETH GOITEIN: So the Posse Comitatus Act, which is an extremely important law in our country, prohibits federal forces from engaging in core law enforcement activities such as arrests, searches, and seizures unless expressly authorized by Congress.

And what the administration is saying is,our forces right now on the ground are not actually engaging in those activities.

And, as of now, that does seem to be the case.

However, reportedly, the troops have been authorized to detain civilians.

That is a core law enforcement activity under the Posse Comitatus Act.

So if and when that starts to happen -- and, frankly, it's hard to see how that doesn't happen if they're going to do more than just stand in A line outside of these federal buildings.

Then we're going to see this claim of inherent constitutional authority butting up against one of the most important laws that Congress has passed, the Posse Comitatus Act, which is a vital safeguard for liberty and democracy.

AMNA NAWAZ: I have just got about 30 seconds left, but I want to ask you about the potential for troops to be deployed in even more cities across the country.

As a legal expert tracking the use of this emergency power, how do you look at that?

ELIZABETH GOITEIN: Well, one of the most alarming things about all of this is that President Trump's memorandum authorizing the deployment of troops is not limited to Los Angeles.

In fact, it doesn't mention Los Angeles.

It authorizes deployment of federal forces anywhere in the country where protests against ICE activity are occurring, regardless of whether those protests involve any violence, and also in places where protests are likely to occur.

That kind of preemptive nationwide deployment is absolutely unprecedented in our history.

That doesn't happen in the United States of America.

AMNA NAWAZ: Liza Goitein of the Brennan Center for Justice, thank you for joining us tonight.

ELIZABETH GOITEIN: My pleasure.