Sanctuary Cities are nothing more than holding pens for prey for Illegal Alien Criminals.  Never mentioned is the existence of the U Visa which protects Illegal Aliens who report or are a victim of crime.  I wonder why?

https://www.nytimes.com/2017/05/08/us/legal-immigrants-who-oppose-illegal-immigration.html?_r=2
U.S.Sanctuary Bills in Maryland Faced a Surprise Foe: Legal Immigrants

"The failure of the sanctuary bills in Maryland reveals a potentially troublesome fissure for Democrats as they rush to defy Mr. Trump. Their party has staked out an activist position built around protecting undocumented immigrants. But it is one that has alienated many who might have been expected to support it."

Obama administration has admitted that Sanctuary Cities are a problem:
http://culberson.house.gov/uploadedfiles/doj_february_23_letter.pdf