There are now 340 "sanctuary" cities throughout the US and counting. How will this impact law enforcement?

Steinle, 32, was killed July 1 while walking with her dad along a San Francisco pier. The suspect, Juan Francisco Lopez-Sanchez, had a felony record and had been deported five times -- but despite a federal immigration detainer request, the city sheriff released him once an old marijuana charge was dropped. San Francisco is among hundreds of so-called sanctuary cities that do not cooperate fully with federal immigration officials
The White House, though, claimed in a written statement that the bill "fails to offer comprehensive reforms needed to fix the Nation's broken immigration laws and undermines current Administration efforts to remove the most dangerous convicted criminals and to work collaboratively with State and local law enforcement agencies."

http://www.foxnews.com/politics/2015/10/20/republicans-push-for-sanctuary-city-crackdown-in-key-senate-vote/?intcmp=hpbt1