Sanctuary cities are against federal law. The problem is that the feds are not enforcing the laws.
Future voters. The Democrats view illegals as future dependent, social services-slurping voters.
The Federal Government has no intention of enforcing immigration laws as the rank and file Border Patrol are being told what to do by Globalist Marxist thugs like Nappy, My Peeps and the Mumbling Muslim...and endorsed by Jorge Bush and Lindsay Grahamnesty.