Donald Trump contends many immigrants in the country illegally pose a threat to public safety. During his presidential campaign, he routinely cited cases of Americans killed by people he said shouldn't have been in the country.
There are cities and counties across the United States that choose not to actively assist federal authorities in carrying out immigration enforcement duties, arguing that such practices negatively impact police-community relations, and that ultimately it's not their responsibility to enforce federal laws. Some studies have also shown that immigrants, regardless of legal status, are less inclined than native-born individuals to commit crimes.
But undocumented immigrants still commit some crimes, so Trump wants to cut all federal funding to places unwilling to help immigration authorities.
"We will end the sanctuary cities that have resulted in so many needless deaths," Trump said during a speech on immigration in Phoenix in August 2016. "Cities that refuse to cooperate with federal authorities will not receive taxpayer dollars, and we will work with Congress to pass legislation to protect those jurisdictions that do assist federal authorities."
WHY HE'S PROMISING IT
Trump says thousands of Americans have been killed by immigrants illegally in the country and that immigration laws must be enforced to prevent future crimes.
Some people who should've been deported are not being turned over from local to federal authorities because of "sanctuary" policies, Trump says.
Sanctuary cities (which can be a town, county or other jurisdiction) limit their assistance to federal immigration authorities seeking to apprehend and deport immigrants in the country illegally.
WHAT NEEDS TO HAPPEN
Trump has said he will cut federal funding to sanctuary cities during his first day in office, but he has not said what specific measure he would take to do so.
Congress can help Trump carry out his promise by passing laws that defund sanctuary cities.
Sen. Pat Toomey, a Republican from Pennsylvania, introduced a bill in June 2016 called the Stop Dangerous Sanctuary Cities Act. Though the bill failed to advance in the Senate, it attempted to block sanctuary jurisdictions from getting grants under certain economic and community development programs.
An identical bill has been introduced in the House and referred to the Subcommittee on Immigration and Border Security.
HOW MUCH WILL IT COST
There are more than 500 counties and cities with policies not to assist U.S. Immigration and Customs Enforcement, according to the Immigrant Legal Resource Center. That number fluctuates as jurisdictions drop or adopt practices.
The amount of money "sanctuary" jurisdictions get from the federal government varies. For instance, New York City this fiscal year is set to receive about $7.7 billion in federal categorical grants (for specific programs).
The mayor of Santa Fe, N.M., said his city gets about $6 million a year in federal grants, with some of those funds going toward senior services and affordable housing.
Boston gets about $250 million a year from the federal government.
WHAT'S STANDING IN HIS WAY
Mayors across the country are resolute to continuing sanctuary policies, despite Trump's threat to block money to them.
New York City Mayor Bill de Blasio has noted that a 1987 Supreme Court case, South Dakota vs. Dole, may restrict Trump's ability to cut funding "across the board."
That case 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.
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, Richard Primus, a law professor at the University of Michigan previously told PolitiFact.
Trump has promised to cancel all federal funding to sanctuary cities on his first day in office, but has not said what action he'll take to achieve that.
The power to disburse government funds rests with Congress, not the president.
Congress may pass laws that support Trump's goal, but a timeline for their enactment depends on legislative support. Congressional action to restrict all federal funds to sanctuary cities may also face constitutional challenges if they don't meet criteria defined by South Dakota v. Dole.