A U.S. Department of Justice lawyer appears to face an uphill battle in persuading a federal appeals court panel to overturn a lower court’s ruling blocking the Trump Administration’s efforts to keep grant money from sanctuary cities, including Chicago.

Chad Readler, a U.S. Justice Department lawyer, was repeatedly grilled by one of three U.S. 7th Circuit Court judges hearing the appeal at the Dirksen Federal Building Friday.

“What a slippery slope you are arguing for,” Judge Ilana Diamond Rovner said at one point, after Readler argued the U.S. attorney general has the authority to impose “special conditions” when it doles out grant money to local jurisdictions.

A little later, Rovner asked Readler: “Where’s the separation of powers? What’s going on?”

To which Readler replied, “This is a voluntary grant the city can accept or not accept.”

Last September, U.S. District Court Judge Harry Leinenweber sided with the city of Chicago in its lawsuit against U.S. Attorney General Jeff Sessions. Leinenweber issued an injunction, saying the administration can’t withhold law-enforcement grant money from sanctuary cities that refuse to follow tough new Justice Department immigration requirements, including giving federal agents access to municipal jails.

Another condition requires the city to give the feds, when requested, a 48-hour heads up of the scheduled release date and time “of an alien in the jurisidiction’s custody.”

Leinenweber’s injunction has a national reach.

On Friday, appellate Judge Daniel A. Manion asked a lawyer for the city why the injunction needed to apply nationally.

“There’s no reason to think the legal issues are restricted to Chicago,” said city attorney, Benna Ruth Solomon.

After Friday’s hearing, Mayor Rahm Emanuel issued a statement in which he said: “Chicago stands proudly with welcoming cities, counties and states across America against the Trump administration’s false choice between our values and our public safety. Chicago will continue to use every legal path available to stand up for our residents, protect our rights and defend our values by standing up to the Trump Justice Department.”

It was not immediately clear when the appeals court is expected to issue a decision.