What are sanctuary cities, and how are they being targeted by Trump?

Trump has promised to fix the immigration system in the US by carrying out mass expulsions. Yet certain cities across the country – known as “sanctuary cities” – have policies that limit cooperation with federal immigration officials. FRANCE 24 spoke to Muzaffar Chishti, director of the Migration Policy Institute at New York University’s School of Law, on how some local governments respond to the crackdown.