New York City Mayor Bill de Blasio isn’t backing away from policies that protect immigrants living illegally in the country, even if that means cuts to his city’s budget.

President-elect Donald Trump has said he will block federal funds to cities with policies or laws that limit their assistance to immigration authorities. New York is among jurisdictions considered a "sanctuary city."

The Democratic mayor was asked on WNYC’s The Brian Lehrer Show how funding would be affected if Trump follows through on his promise.

"I think the first thing is to recognize that from what I know so far because of a decision by the Supreme Court, no president's in a position to cut off funding across the board. It has to be very specific to the matter at hand," de Blasio said. "If we disagree in one particular policy area, there may be opportunities for the federal government to say, ‘well we are not going to fund you in that policy area,’ but not across the board."

As other mayors across the country stand behind their immigrant-friendly policies, we wondered about de Blasio’s comment on how much is at stake.

Can funding be restrained in certain areas but not "across the board," as de Blasio said?

A key Supreme Court case

The mayor’s press office told us he was referring to the 1987 landmark case South Dakota vs. Dole, which the mayor’s press office concluded "that federal conditions have to be reasonable and related to the programs they are attached to."

South Dakota vs. Dole examined whether Congress exceeded its spending powers and violated the 21st Amendment (allowing states to regulate alcohol) by setting conditions for states to receive federal highway funds.

Congress in 1984 enacted legislation that allowed the secretary of the Transportation Department to withhold 5 percent of federal highway funds from states where the minimum drinking age was below 21. South Dakota allowed 19-year-olds to buy alcohol.

In a 7-2 decision, the Supreme Court determined that Congress within constitutional bounds "acted indirectly under its spending power to encourage uniformity in the states' drinking ages."

The court also said spending power must be in pursuit of "the general welfare." Conditions set by Congress for the disbursement of funds must also be unambiguous, related to the national project or program, not lead to unconstitutional actions and not be coercive, the court affirmed.

Constitutional law experts told us de Blasio’s comment is generally sound, but noted that the Dole case is specifically about congressional spending power, not presidential authority.

"If Trump was referring to the possibility of congressional legislation that would make continued funding contingent on cooperation with federal immigration policy, then we have a possible Dole situation," said Christopher W. Schmidt, a law professor and co-director of the Institute on the Supreme Court of the United States at Chicago-Kent College of Law, Illinois Institute of Technology.

Imposing across-the-board spending cuts for "sanctuary cities" would run afoul with at least one of the criteria set in the 1987 Supreme Court case — that conditions on spending be related to the national program that Congress is seeking to advance, said Franita Tolson, a professor at Florida State University College of Law.

For instance, if the federal government gives New York money for mass transit, and New York doesn't want to participate in a federal initiative for education, the federal government can't in turn threaten the mass transit funds, said Richard Primus, a law professor at the University of Michigan.

Trump’s administration "can’t cut off any federal grants to sanctuary cities unless it can show that those grants were clearly conditioned on cooperation with federal deportation policies," Ilya Somin, a law professor at George Mason University, wrote in an opinion piece published by the Washington Post.

Conditions for funds also cannot be so great that the threat of losing federal money amounts to coercion, Primus said.

Scholars pointed to the 2012 Supreme Court case National Federation of Independent Business vs. Sebelius, in which seven of the nine justices said it would be unconstitutionally coercive for Congress to withdraw Medicaid funds from states refusing to participate in the Medicaid expansion under the Affordable Care Act.

"One might argue that the larger the amount of money at stake (or the ‘broader’ the threatened cut), the more coercive the condition, but there are other factors to be taken into account as well," said Lana Ulrich, associate in-house counsel at the National Constitution Center.

In the case of sanctuary cities, spending power might be interpreted differently, Ulrich said.

At issue might be the extent to which Congress may condition grants or whether Congress has the discretion to withhold funds for cities that are not in compliance with federal law," Ulrich said.

Trump has not outlined extended details on his sanctuary city proposal, but he said that cities that refuse to assist federal authorities "will not receive taxpayer dollars."

Our ruling

In a discussion about Trump’s plans to cut federal funding to sanctuary cities, de Blasio said, "because of a decision by the Supreme Court, no president's in a position to cut off funding across the board. It has to be very specific to the matter at hand."

It’s not as settled by law as de Blasio makes it sound, but experts say generally that the mayor is correct.

The Supreme Court, in South Dakota vs. Dole, concluded that Congress could not coerce local governments to act based on the threat of withholding federal funds. Also, any funds that are withheld must be germane to the reason they are being withheld.

The court ruling dealt with Congress, however, and not the executive, and there is ambiguity about both what tactic Trump might pursue and the legal precedence behind it.

De Blasio's statement is accurate but needs clarification or additional information. We rate de Blasio’s claim Mostly True.