Pennsylvania’s Republican Sen. Pat Toomey, fresh off winning the re-election battle of his life, stood on the Senate floor Wednesday and asked Donald Trump to strip some federal funding away from the largest city in the state he represents.

Philadelphia is what’s called a “sanctuary city.” Mayor Jim Kenney prefers the term “Fourth Amendment City.” Either way, what it means is that law enforcement in the city of Philadelphia will not detain undocumented immigrants at the request of federal immigration officials unless the person is a convicted violent criminal.

Toomey and many of his allies, including the president-elect, say the policy is dangerous and allows criminals to walk free. This week on the Senate floor, Toomey rattled off three examples from Philadelphia of undocumented immigrants who were released from police custody and went on to commit dangerous crimes.

The senator was pushing his bill that would strip away certain grants from so-called sanctuary cities like Philadelphia (and San Francisco and Chicago and New York, etc.). But Toomey also called on Trump to take executive action against those cities when he steps into office on Jan. 20 by stripping away some federal funding from those jurisdictions.

“He could issue an executive order which would, I think, significantly limit dangerous sanctuary cities,” Toomey said, adding: “It would be a good start, and it would be fully consistent with his constitutional powers.”

Kenney has vowed that Philadelphia will remain a sanctuary city. Other mayors have said the same. The administration has said it’s not discussing details because, at this point, it doesn’t know what Trump will do when he enters office.

Let’s be clear: What Trump may do could be a devastating financial blow to the city of Philadelphia. But what he will do is a much different story.

What Trump can do

It’s still not all that clear what Trump can do with his executive powers in terms of unilaterally stripping away funding from sanctuary cities, like he vowed to do on the campaign trail.

“Block funding for sanctuary cities. We block the funding. No more funding,” Trump said during an August rally in Phoenix. “Cities that refuse to cooperate with federal authorities will not receive taxpayer dollars.”

Still, Kenney has remained resolute when it comes to Philadelphia’s status.

“First of all, we’ve changed the name from ‘sanctuary city’ to ‘the Fourth Amendment city,'” Kenney told The Inquirer. “We respect and live up to the Fourth Amendment, which means you can’t be held against your will without a warrant from the court signed by a judge. So, yeah, we will continue to be a Fourth Amendment city abiding by the Constitution.”

Taking away all federal taxpayer dollars from Philadelphia and similar cities because they are sanctuary cities probably isn’t possible. Any such move would almost definitely result in a court battle over the viability of sanctuary cities and whether or not the federal government can actually prevent them from receiving federal dollars.

“In terms of him completely defunding sanctuary cities by not giving them any funding whatsoever, it would be virtually impossible to do,” Phil Torrey, a lecturer at Harvard Law School, told the New York Daily News.

What’s up for debate — and what would likely be at the center of a court challenge against the administration if Trump were to follow through — is what funding and grant money can actually be taken away from cities that don’t comply with federal detainer requests from Immigration and Customs Enforcement.

The Supreme Court has held that if Congress or an administration wants to take away federal funding from a municipality or state based on certain conditions, the funding has to at least be reasonably related to those conditions.

Federal funding in Philly

If Trump wanted to take away all federal dollars from the city of Philadelphia including grant money, he and his administration would be stripping the city of millions of dollars a year in grant money that goes toward supporting the most vulnerable Philadelphians.

We’re talking HIV/AIDS patients. The homeless. Low-income mothers and children. Victims of domestic violence. The elderly. Foster children. People afflicted by addiction and disease and gun violence. The city would lose funding it uses to prop up its affordable housing infrastructure, and it would lose millions more in STD prevention programming and after-school programs and beds for homeless shelters and child protective services.

There’s almost no way Trump’s administration could take that grant money from Philadelphia, as it’d be a tough sell to claim that these grants are even reasonably related to the city’s refusal to share information with federal immigration officials.

What he could consider is taking away Department of Justice funding to sanctuary cities, or even certain DOJ funding. In July, the Justice Department — under President Obama, no less — decided cities that didn’t comply with detainer requests could be subject to losing eligibility for certain grants, including the State Criminal Alien Assistance Program that reimburses cities for fighting illegal immigration and the Justice Assistance Grant.

Philadelphia has received about half a million dollars in SCAAP grants in the last five years. In fiscal year 2016, the city was awarded more than $1.6 million in Justice Assistance grants and has won nearly $9 million from them in the last five years. Trump could try to go a step farther and take away all Department of Justice funding from sanctuary cities.

In recent years, Department of Justice grants were set to fund or reimburse programs like:

Domestic violence arrest and enforcement support

DNA backlog reduction (read: testing rape kits)

State Criminal Alien Assistance Program

Drug violence intelligence initiatives

Bulletproof vests for police officers

Re-entry programs

Youth violence prevention

Performance-based prosecution projects

The DOJ also allocates millions of dollars worth of grant funding to cities from the federal forfeiture program which is used largely to fight illegal narcotics sales. So it’s safe to say police (and the DA’s office and women and those who fight for programming for formerly incarcerated individuals) wouldn’t be too happy with such a move by the Trump administration. The National Association of Police Organizations has already come out against it.

“While NAPO supports efforts in Congress to eliminate sanctuary jurisdictions, which pose real threats to the American people,” the organization said in a statement, “we do not believe that law enforcement should be punished for the decisions of elected officials.”

What if Toomey’s bill passes?

Toomey’s bill is a much more tailored approach at curbing sanctuary cities. His bill was actually approved last year by a majority of the U.S. Senate, but it didn’t cross the 60-vote threshold to break through a filibuster by Senate Minority Leader Harry Reid. Now, Toomey — who made sanctuary cities a major part of his recent campaign — wants it up for reconsideration.

His bill would make sanctuary cities ineligible for Economic Development Administration Grants and the more popular Community Development Block Grants. More than $3 billion was allocated through the latter grant last year, and Philadelphia itself received $38.8 million worth of Community Development Block Grants this fiscal year.

While that’s a small fraction of the city’s overall budget, it’s a major portion of the funding that goes toward the city’s Office of Housing and Community Development. According to the office’s consolidated plan, that office relies on just 1 percent of its funding from the city. The rest comes from state and federal grant funds largely in the form of Community Development Block Grants.

So what’s it mean for Philly if those grants are no longer there? It could lose millions of dollars per year in funding that goes almost entirely toward affordable and subsidized housing initiatives as well as programming that works to fight blight. In fact, Community Development Block Grants are required to be spent almost entirely on low-income programming and initiatives.

Toomey still contends his bill — which also shifts all liability for detainers onto the federal government — will “solve the problem.”

“While we await the opportunity to enact this legislation,” he said, “I hope that our new president will take the executive order steps he can to at least diminish this problem.”