“The Cook County legislation was very critical and a part of the development for the legislation in the District of Columbia,” said Ron Hampton, a retired Metropolitan Police officer in the nation’s capital who has pushed the D.C. bill.

Hampton pointed to a legal opinion that supporters of the Cook County measure obtained from State’s Attorney Anita Alvarez’s office last year. That opinion, citing a federal court ruling in Indiana, called detainer compliance voluntary and helped convince the Cook County Board to approve the ordinance. Hampton said the opinion added weight to what he called “a model piece of legislation.”

Since the Cook County ordinance passed, New York City, the state of Connecticut and the California county of Santa Clara have also curtailed their compliance with immigration detainers.

On July 5, the California Senate approved similar legislation that would affect the entire state. That bill is expected to pass the state Assembly. Gov. Jerry Brown has not indicated whether he would sign it into law.

At a hearing Tuesday, Rep. Candice Miller (R-Michigan) said Secure Communities had “excellent buy-in” from jurisdictions across the nation. Miller, chairwoman of the Homeland Security Subcommittee on Border and Maritime Security, called Cook County “the big holdout” and asked Morton about it.

Morton repeated an administration claim that Cook County’s disregard of ICE detainers compromised public safety. That claim was the subject of a WBEZ investigation completed in May. Inmates freed as a result of the ordinance, the investigation found, have not reoffended or jumped bail more than other former inmates have.

Morton also told the subcommittee about letters he had written to Cook County Board President Toni Preckwinkle to spell out his concerns. “We have been working with the county to see if there isn’t some solution,” Morton said. “I won’t sugarcoat it. I don’t think that that approach is going to work in full. We’re going to need the help of others. We have been exploring our options under federal law with the Department of Justice.”

Morton said he would also push for a cutoff of some federal funds for the county’s jail.

That vow won praise from Miller. “I can’t tell you how delighted I am,” she said. “If they’re not going to assist us in removing not only criminal aliens but those that might go on to commit a terrorist attack or what-have-you, because they want to have their city become a sanctuary, the federal government cannot stand by idly and allow that to happen.”

As other jurisdictions adopt the Cook County approach, some enforcement advocates are calling for a tougher federal response.

Ira Mehlman, spokesman of the Washington-based Federation for American Immigration Reform, points out that the Obama administration has sued states such as Arizona and Alabama for taking immigration enforcement into their own hands

“Yet, when it comes to jurisdictions that have openly defied federal enforcement, then the Justice Department seems to have enormous patience and is extremely lenient,” Mehlman said.