House Oversight Committee Chairman James Comer (R-KY) sent letters Johnson and the mayors for three other major cities – Boston, Denver, and New York – last week, asking them to testify before the committee and hand over all documents and communications related to their city's sanctuary policies.

The US justice department has filed a lawsuit against Chicago, accusing local officials of impeding federal immigration enforcement efforts amid Donald Trump's drive to ramp up deportations.

The Trump administration is suing Chicago over what are known as sanctuary laws. The administration claims the nation’s third-largest city “thwarts” federal efforts to enforce immigration laws.