Mayor Bill de Blasio convened an emergency press conference on Wednesday night to address President Donald Trump's executive order threatening to strip federal funding from "sanctuary cities," i.e. cities where local law enforcement and city agencies generally don't cooperate with federal immigration authorities. He emphasized that the order is "vague" in its language, and that New York City is prepared to challenge it in court.

"We are immediately struck by how vague it is, and how subject to challenge it is," de Blasio told reporters.

"The stroke of a pen in Washington does not change the people of NYC or its values," he added, insisting that, "We're not going to allow our police officers to be used as immigration enforcement agents. It's as simple as that."

The executive order, which President Trump signed this afternoon, states the following:

[T]he Attorney General and the Secretary, in their discretion and to the extent consistent with law, shall ensure that jurisdictions that willfully refuse to comply with 8 U.S.C. 1373 (sanctuary jurisdictions) are not eligible to receive Federal grants, except as deemed necessary for law enforcement purposes by the Attorney General or the Secretary.

Zachary Carter, legal counsel to the mayor, pointed to the phrase "to the extent consistent with the law."

"There are hedges embedded right in the order itself," he said.

"We believe we are on solid ground for a legal challenge," de Blasio added. He referenced the 2012 Supreme Court ruling in National Federation of Independent Business v. Sebelius, which found that the federal government could not withhold unrelated funding from states unwilling to comply with a federal mandate.

But even as he insisted that the executive order has weak legs, de Blasio offered his understanding of where funding could be cut, based on his office's perusing the order. If President Trump were able to withhold federal funding from New York City, he predicted, it would hit the NYPD the hardest.

NYPD Commissioner Jimmy O'Neill echoed the concern, estimating somewhere between $150 and $160 million in federal cuts to anti-terrorism efforts, including bomb squad training, security cameras and overtime, as well as security for the United Nations, and, ironically, Trump Tower.

Even this was hedged, though, as de Blasio acknowledged language in the order indicating that federal grants could be withheld with the exception of law enforcement funding. "This order is written in a very vague fashion," he reiterated.

The city's next fiscal year budget, a preliminary version of which was presented this week, calls for $7 billion in federal funding. Budget experts say most of that money goes towards programs that serve low-income families.

"Federal funding goes predominantly toward social services, education and health," Maria Doulis, director of city studies for the Citizens Budget Commission, told Gothamist this week. "To the extent that the federal government pulls back on these things, it will put pressure on the state and the city. And there is a limit to how much the city can do to address these needs on its own."

Other elected officials took the podium on Wednesday, stating their intention to defy Trump's efforts to deport. There are an estimated 500,000 undocumented immigrants in New York City. However, as DNAInfo points out, the order refers to 'aliens,' a category that includes legal immigrants and those with green card status, or asylum.

"If there was ever any doubt in anyone's mind whether Donald Trump's hateful, bigoted rhetoric truly reflected his intentions, today's executive orders confirm that his agenda will take our country down a dangerous and divisive path," said City Council Speaker Melissa Mark-Viverito.

"Although there are many unknowns, one thing is certain," she added. "The City Council's commitment to protect our city is unwavering."

Democratic Congressman Joe Crowley (eastern Bronx and north-central Queens) alluded to New York's role as a major contributor to federal coffers.

"We give more to the feds than we get back," Crowley said. "And you know what? New Yorkers are getting tired more and more that we are a donor state, and we have other states electing people like Donald Trump who then come in and dictate to us that we're going to get less than we deserve to keep our people safe."

Attorney General Eric T. Schneiderman, whose office issued legal guidance last week for sanctuary jurisdictions, also accused President Trump of making empty threats this afternoon.

The NYPD is not, it's important to note, severed from Immigration and Customs Enforcement. 'Sanctuary city' status only curtails ICE intervention. Early in Wednesday's press conference de Blasio held up a list of 170 offenses that the NYPD has cooperated with homeland security on since 2014. These wide-ranging offenses, broadly categorized as "public safety concerns," include criminal sale of a controlled substance, burglary, trespass, rape, murder, and vehicular manslaughter, among others. De Blasio referred to the list as "a middle ground that works."

Immigrants with green cards and permanent resident status are also subject to deportation if for committing broken windows offenses like turnstile jumping.

When a reporter asked the mayor if he would scale back on broken windows policing in the face of an emboldened ICE, he deferred.

"Look, let’s take one thing at a time here," de Blasio sad.

Also today, Trump signed an executive order for the construction of a wall along the United States border with Mexico. He’s expected to issue another barring refugees from Middle Eastern countries—a move that thousands of New Yorkers are currently protesting, among other things.

[Update 1/27]: This piece has been updated with the mayor's response to a question about broken windows policing.