This Sanctuary City phenomenon didn't start on Obama's watch it started back in1980 on Reagan's watch.
The Sanctuary movement wasn't meant make US cities safe harbors for illegal aliens, it was initiated by various diverse religious organizations which banded together to oppose the deportation or forced repatriation of refugees fleeing Civil war and persecution in their homelands.
Your Senate Republicans know the history even if you don't. And they also know that the Sanctuary Movement does NOT preclude ICE or any other federal immigration agency from apprehending illegal aliens in those cities you call Sanctuary Cities. They also know that municipalities , counties and states are not required to enforce federal law and, in this case, the courts have held that when the spheres of jurisdiction are abrogated in that way, the 4th Amendment is violated.
Some have confused “sanctuary city” policies with the notion that immigrants in these communities are insulated from any immigration enforcement action against them. In fact, nothing in a so-called sanctuary city policy prevent federal enforcement actions. Some cities and localities—including San Francisco—have used the term “sanctuary” in their community policing policies in solidarity with the movement of the 1980s.
So What is it about the Sanctuary Movement that drives Republican politicians to want to ban it? BUt banning isn't an option, so they want cut Federal law enforcement funding for so -called Sanctuary Cities that
Senate Democrats have temporarily blocked a measure that would deny federal law enforcement funds to so-called "sanctuary cities," where local authorities don't automatically report undocumented immigrants without a record of serious criminal offenses to federal Immigration and Customs Enforcement (ICE) agents. The idea for the bill was raised and enthusiastically promoted by figures on Fox News, who urged Republicans to "starve" these cities of federal money, despite experts noting that defunding would hurt public safety and evidence showing that so-called "sanctuary cities" are not actually a "safe haven" for undocumented immigrants and, in fact, deter criminality.
Congress' Attempt To Cut Federal Funds For "Sanctuary Cities" Was Built On Fox News' Rhetoric
Immigrant advocates maintain that sanctuary cities are effective because they allow undocumented immigrants to report crimes that they otherwise would be hesitant to come forward to talk about. A 2015 National Latin@ Network for Healthy Families and Communities survey found that 41 percent of foreign-born Latinas interviewed reported that they were afraid to call the police or go to court because they feared they could be deported.
http://thinkprogress.org/immigration/2015/07/23/3683375/repub-bills-sanctuary-cities/
I stand with the Democrats on this one. The Republicans are evil bastards who don't mind jeopardizing the safety of entire communities by defunding their local law enforcement agencies of "Sanctuary Cities."