Leinenweber apparently agreed, saying in his ruling that Sessions had attempted an "unprecedented seizure of power" in imposing such conditions on law enforcement grants, The Chicago Sun-Times reported.
The decision marks the latest in a swift turn of events.
The Justice Department funding would have been just a small fraction of Chicago's overall budget, but Mayor Rahm Emanuel said it was important for the city to maintain its "status as a welcoming city" to immigrants. First, Congress blocked him from using federal funds to crack down on legal weed, then everybody found out about Donald Trump addressing him in the Oval as an "idiot", and now a federal judge has blocked one of dude's few remaining reasons for sticking around a White House that hates him - screwing over sanctuary cities.
As part of that policy, the Justice Department has sought to punish cities and other local jurisdictions that have joined a growing "sanctuary" movement aimed at shielding illegal immigrants from stepped-up deportation efforts. President Trump later announced that he was working on an agreement to protect them.
For months there's been an immigration crackdown. Earlier this month, Sessions announced that the administration would end a program that protects young immigrants who were brought to the US illegally as children or came with families who overstayed their visas. The Trump administration, on the other hand, has accused sanctuary cities of putting politics over public safety.
Trump on Friday took a hard line against allowing close family members of new immigrants to follow those immigrants to the U.S.
Attorney General Jeff Sessions during a press conference. A number of cities and police chiefs around the country argue that cooperating with such requests could jeopardize the trust police need to have with local communities, and in some cases could place departments in legal gray areas. Philadelphia, San Francisco, and California have filed suits similar to Chicago's.
"They have demonstrated an open hostility to enforcing laws created to protect law enforcement - federal, state, and local - and reduce crime, and instead have adopted an official policy of protecting criminal aliens who prey on their own residents", Sessions said after Chicago's lawsuit was announced.
Sessions described Chicago's lawsuit in August as "astounding".
But that approach isn't seeing much sympathy in court. Total funding for such grants this year was $383.5 million, according to the Justice Department. "Once such trust is lost, it can not be repaired through an award of money damages".