The Department of Justice has singled out and distributed a missive to nine jurisdictions alerting them to the financial consequences of continuing to shield illegal immigrants. According to the DOJ, “The letters remind the recipient jurisdictions that, as a condition for receiving certain financial year 2016 funding from the Department of Justice, each of these jurisdictions agreed to provide documentation and an opinion from legal counsel validating that they are in compliance with Section 1373.”

That law stipulates: “[A] Federal, State, or local government entity or official may not prohibit, or in any way restrict, any government entity or official from sending to, or receiving from, the Immigration and Naturalization Service information regarding the citizenship or immigration status, lawful or unlawful, of any individual.” You’ll recall last month when Attorney General Jeff Sessions pre-empted Friday’s action: “The Department of Justice will require that jurisdictions seeking or applying for DOJ grants to certify compliance with [U.S. Code 1373] as a condition of receiving those awards.” Obviously, Sessions is signaling that he isn’t bluffing on the sanctuary city crackdown.

To be clear, “These letters are not demanding that police and municipal governments assist Immigration and Customs Enforcement (ICE) in rounding up illegal immigrants subject to deportation orders,” Reason’s Scott Shackford explains. “The federal government cannot force cities to help them enforce immigration laws. It’s important to understand that, just as they can’t force cities to enforce the federal ban on marijuana possession or consumption.”

Shackford adds, “There is, however, a federal immigration regulation that this small group of cities may be violating. Federal regulations forbid any state or local government from prohibiting its employees from communicating with the feds about any person’s immigration status. So, for example, if a local police officer arrests somebody he knows is an immigrant in the United States illegally, he cannot be prohibited from passing that information along to ICE. The targets of these letters are cities — New Orleans, Miami, Chicago (and Cook County), Philadelphia, Las Vegas, Milwaukee, New York City, Sacramento (California) — that have policies or ordinances that prohibit this communication.”

And that defiance is a big reason the DOJ says that “many of these jurisdictions are … crumbling under the weight of illegal immigration and violent crime.” These jurisdictions are actively shielding illegal immigrants, some of whom are felonious. And by doing so they are essentially telling officers of the law to disregard their conscience. That’s a total disregard for Rule of Law.

Words matter. And when word gets around that jurisdictions will defy immigration statutes, it only emboldens illegal immigrants. But words matter when it comes to enforcement too. Donald Trump’s and Sessions’ hardline stance on illegal immigration is the driving force for why illegal border crossings are down significantly. In that sense, the status quo has already been shattered. And cities that pretend otherwise do so at their own peril.