For months, Donald Trump has been fueling panic about Chicago's crime rate, repeatedly threatening to use his power as president to "send in" federal troops to deal with the scourge of homicides plaguing the city.

On Monday, Chicago made its own power move.

The city filed a federal lawsuit against the Trump administration in an effort to stop the Department of Justice, led by Trump's frenemy Jeff Sessions, from punishing Chicago for its status as a so-called sanctuary city. In defending the lawsuit on CNN, Mayor Rahm Emanuel stressed that forcing his city to choose between its values and the police department's community policing philosophy is "a false choice" that "undermines our actual safety agenda." Going after Trump and Sessions over policing is also likely a welcome change for Emanuel, who has drawn harsh fire for Chicago's police brutality and persistently high violent crime.

The lawsuit centers on a federal grant, the Edward Byrne Memorial Justice Assistance Grant—or Bryne JAG—used by state, city, and tribal governments to support law enforcement. In July, Sessions—a longtime foe of undocumented people—took his first real step to crack down on sanctuary cities when he announced that he would be imposing new conditions on localities that want to receive cash from the Bryne JAG.

Chicago's lawsuit alleges that these new conditions—which empower the feds to interrogate arrestees at local jail facilities and require local law enforcement officials to detain individuals longer than justified by probable cause—are "unauthorized and unconstitutional." Meanwhile, the city received $2.3 million from the Bryne JAG last year.

Desus and Mero have their own take on the president's weird fondness for threatening Chicago:

While Sessions has already responded to Chicago's legal challenge by saying that the Windy City "has chosen deliberately and intentionally to adopt a policy that obstructs this country's lawful immigration system," a number of legal experts have argued the lawsuit's central claims actually rest on sturdy shoulders. George Mason Law School professor Ilya Somin told me that while it's not unusual to see a presidential administration attempt to finagle grant conditions, he's "not aware of a case as blatant as this one where the executive branch just seems to make up conditions on its own, and doesn't even have a minimally plausible argument that they were included in the bill Congress passed."

Likewise, Phil Torrey, an attorney focused on the intersection of criminal and immigration law at the Harvard Immigration and Refugee Clinical Program, thinks Chicago's suit has some real muscle. Here's what he had to say about the latest major lawsuit against the Trump administration and how this saga might play out from here.

VICE: What do you make of Chicago's new lawsuit? Is it viable?

Phil Torrey: I think Chicago feels like they've been backed into a corner as they anticipate potentially losing JAG funding. They make a number of claims—on statutory and constitutional grounds—and I'd say both have a good deal of merit.

What are some of the stronger claims?

Well, there are a few. One is Chicago's spending clause claim: Basically what the city is saying is that the executive agency responsible for administering these federal grants cannot impose additional restrictions on those funds without congressional approval. And in this instance, Congress has not given any authority to the DOJ to impose the kinds of restrictions Sessions is advocating for. I think that's a pretty clear, straightforward argument.

I also think the city of Chicago and other municipalities are currently in compliance with federal law, specifically Section 1373 [a federal statute that bars local governments from restricting the sharing of immigration status information with ICE agents]. If you look closely at their "sanctuary" policies, you'll see they don't have rules that restrict the sharing of this information. I think the DOJ is incorrectly construing those policies to claim cities are running afoul of the law.

But if Chicago is arguing that the DOJ needs congressional approval to condition federal funds, couldn't the GOP-controlled Congress just go ahead and do that, and effectively render the lawsuit moot?

Yes. Congress could attempt to pass some legislation that would further restrict JAG funding, but that hasn't been done yet. There could be other constitutional challenges to that kind of statute, but as it stands, that specific enabling language to allow the DOJ to pass new restrictions has not been approved.

One complicating factor is that the Bryne JAG is related to public safety, and Congress can't impose its will on municipalities in a way that would force them to implement new public safety measures. Constitutionally, public safety is completely within the purview of a city or county or state, and Congress could arguably be overstepping its authority if it passes legislation that forces these localities to do something that they believe harms their public safety.

Do you think other local governments will follow Chicago's lead, as some reports suggest they are considering?

You've got city, county, and state law enforcement officials all serving different roles within the realm of public safety, and some of these new conditions placed on the Bryne JAG funding affect those players in different ways. You could definitely imagine multiple levels of local government filing claims—either in conjunction with Chicago or separately against the DOJ.

Can't the administration argue—with some merit—that the federal government has broad discretion over immigration policy?

This is actually being framed more as a public safety issue than an immigration enforcement issue. And when you're operating within the realm of public safety, then states and localities have full constitutional authority to enact and enforce policies that they see fit. Municipalities are saying, "Wait a minute—public safety is our realm to operate in. You can go ahead and enforce immigration laws. Do what you need to do, but don't come in here and tell us how to do public safety."

As this case winds its through the courts, what should we be looking out for next?

Hundreds of municipalities have decided that the best way to police their communities is by separating their public safety enforcement from immigration enforcement. If we move to entangle them, it may have a chilling effect that could really harm community systems.

I think this case illustrates that the administration is putting a target on states, counties, and municipalities that have these types of [community policing] policies—considering them somehow against federal law. Essentially what the DOJ is doing is saying, "We're going to substitute your own views on what's best for your communities with our views."

You effectively have a federal government attempting to force municipalities to change their policies, which is actually contrary to how you'd expect a traditional Republican, conservative government to act. Normally you'd expect to see conservatives favoring local autonomy and disfavoring federal overreach. That's not what's happening.

This interview has been lightly edited for length and clarity.