It said in a news release that New York City's gang murders are "the predictable effect of the city's "soft on crime" stance".
"President Trump and Attorney General Sessions have to make a decision immediately about this statement, because it has denigrated not only the people of New York City, but the men and women of the NYPD", de Blasio said during a news conference.
De Blasio and other top city officials also batted back against the "soft on crime" label in the Justice Department's statement.
"Unfortunately, the Mayor's policies are hamstringing the courageous NYPD officers that protect the city, and only serve to endanger the lives of the hard working men and women of the NYPD who care more about keeping their city and country safe than they do about city hall politics".
"Many of these jurisdictions are also crumbling under the weight of illegal immigration and violent crime", the Justice Department said as it sent the letters.
"Fear mongering and falsehoods will not intimidate our state into compromising our values", Becerra said. They have said that having local police turn in illegal immigrants to federal authorities will make it more hard for the police to gain the trust of communities they need to work with to reduce crime.
"We found that while some (jurisdictions) honor a civil immigration detainer request when the subject meets certain conditions, such as prior felony convictions, gang membership, or presence on a terrorist watch list, others will not honor a civil immigration detainer request, standing alone, under any circumstances", Horowitz says in the memo.
"Milwaukee County has its challenges but they are not caused by illegal immigration", Abele said. The cities which received the threatening letters have until July 30 of this year to provide documentation showing they are in compliance with federal immigration law.
West Ham seek Inzaghi
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And that's exactly what sanctuary cities are counting on. "We're pleading with the cities, let's don't have a fight over this", Sessions said earlier Friday.
"For a long time, Mayor De Blasio and the NYPD's leadership have failed to heed the warning that refusing to cooperate with federal immigration officials when it comes to criminals and suspected terrorists would have consequences beyond making our City less safe". "We always do with a federal grant". Sachs says the effect of the federal government's demands will make the city more risky.
The law that Sessions wants enforced is very narrow, and it would not bar any of the policies that people generally associate with sanctuary jurisdictions.
Each letter was worded similarly and signed by Alan R. Hanson, the acting director of the Office of Justice Programs, which administers the Byrne law enforcement grant program, the federal government's top source of justice funding for local jurisdictions. Cities, though, have said they are anxious that Sessions's threats are not mere talk.
All were singled out by the Justice Department's Inspector General previous year during the Obama Administration. New York City's mayor and Sessions are battling over a Department of Justice statement accusing the city of being "soft on crime".
Immigrant-rights activists have demanded that cities resist the Trump Administration, and have called on more cities to declare themselves sanctuaries.
Associated Press writers Michael Kunzelman in Baton Rouge, Louisiana; Ivan Moreno in Milwaukee; Sophia Tareen in Chicago; Karen Matthews in New York; Amy Taxin in Santa Ana, California; Elliot Spagat in San Diego; and Ken Ritter in Las Vegas contributed to this report.