After the killing of Kate Steinle, shot dead on a pier in San Francisco by an illegal immigrant who had been convicted of seven felonies and deported five times, it would seem almost a no-brainer that Congress would seek to correct the situation in which self-declared “sanctuary cities” like San Francisco defy federal law by refusing to hand over criminal immigrants to federal authorities. After all, who could possibly defend the city’s actions? Even Democrats like Hillary Clinton, Dianne Feinstein, and Barbara Boxer have condemned San Francisco’s efforts to shield multiple-felon Juan Francisco Lopez-Sanchez from Immigration and Customs Enforcement agents. Why not just enact legislation to force San Francisco to obey federal law?

It turns out things are not that simple.