De Blasio and other top city officials also batted back against the "soft on crime" label in the Justice Department's statement.
Mayor's spokesman Seth Stein calls that "alternative facts".
Sanctuary "crackdown" is really NBD, Sessions' lawyers say.
Through April 16 the city had seen 74 killings in 2017, according to the police department, which would put it on pace to have the fewest number of murders since it began keeping accurate records on homicides.
Emanuel, a White House chief of staff in the Obama administration, has beefed up the city's efforts to protect immigrants living in the country illegally, including establishing a legal fund with taxpayer money to help those facing deportation. However, local leaders say they will go against it even if that means losing federal funding. Then there's Trump, who campaigned on a promise to defund sanctuary cities, only to find his immediate power to do so limited.
The big difference, of course, is that while Trump's travel order took effect immediately, the sanctuary city order has yet to concretely impact cities like San Francisco and Richmond, except in budget planning.
Baltimore residents to comment on plan to overhaul police
District Court Judge James Bredar in the ongoing legal case over police reform in Baltimore. A federal judge signed off Friday on the consent decree between the city and the U.S.
The agency cited the rising murder rate in Chicago and cast blame for gang murders in NY on what it labeled a "soft on crime" stance. "Cities that refuse to cooperate with federal authorities will not receive taxpayer dollars".
And when Immigration and Customs Enforcement sends validated requests for information regarding the release of violent criminals from police custody or jail, New York City readily cooperates. He noted that the law referenced in the Justice Department's letter was on the books before President Donald Trump took office.
The Washington Times reports that letters were sent to each of the nine jurisdictions the Justice Department said had signed documents a year ago, when they applied for Byrne Justice Assistance Grant money, saying they complied with a section of federal law that demands cooperation when immigration agents ask for it.
"Attorney General Sessions is supposed to be the leading law enforcement official in America", de Blasio said.
President Donald Trump has vowed to strip federal funds from dozens of state and local governments that do not fully cooperate with US immigration agents, arguing they endanger public safety when they decline to hand over for deportation illegal immigrants who are arrested for crimes.
The grants in question are among the largest handed out under the program, collectively amounting to 11 percent of the $256 million distributed in the last fiscal year.
They were singled out in a May 2016 report by the Justice Department's inspector general that found local policies or rules could interfere with providing information to immigration agents.