A Cook County commissioner is quietly proposing an ordinance that would require the county’s massive jail to release some inmates wanted by immigration authorities.

Sponsored by Jesús García, D-Chicago, the measure would prohibit the jail from holding inmates based on an Immigration and Customs Enforcement request unless they have been convicted of a felony or two misdemeanors, and unless the county gets reimbursed.

The legislation’s preamble says complying with the ICE requests, known as detainers, “places a great strain on our communities by eroding the public trust that local law enforcement depends on to secure the accurate reporting of criminal activity and to prevent and solve crimes.”

The jail now holds detainees requested by ICE for up to 48 hours after their criminal cases would allow them to walk free. Sheriff Tom Dart’s office says the jail turns over about a half dozen inmates to the federal agency each business day.

Dart this month told WBEZ his staff was exploring legal options for releasing some of these inmates. The sheriff said his review began after he noticed that San Francisco County Sheriff Michael Hennessey had ordered his department to quit honoring certain ICE detainers beginning June 1.

If Dart’s office follows Hennessey’s path or if García’s legislation wins approval, Cook County could become the nation’s largest local jurisdiction to halt blanket compliance with ICE holds.

“Cook County would be a counter pole to Arizona’s Maricopa County,” says Chris Newman, general counsel of the National Day Laborer Organizing Network, a Los Angeles-based group that opposes involving local authorities in immigration enforcement.

García’s office didn’t return WBEZ calls or messages about his legislation. The offices of Sheriff Dart and Cook County Board President Toni Preckwinkle said they had seen the bill but declined to say whether they supported it.

A spokeswoman for Cook County State’s Attorney Anita Alvarez said late Tuesday her office had not been consulted about García’s proposal. A 2009 letter from Alvarez to Dart’s office said federal law required the sheriff to comply with “any ICE detainers.”

In recent months, however, immigration authorities have acknowledged that local jails do not have to comply with the detainers.

ICE spokeswoman Leticia Zamarripa, asked for comment about García’s legislation, sent a statement calling the detainers “critical” for deporting “criminal aliens and others who have no legal right to remain in the United States.”

“Individuals arrested for misdemeanors may ultimately be identified as recidivist offenders with multiple prior arrests, in addition to being in violation of U.S. immigration law,” the ICE statement said. “These individuals may have been deported before or have outstanding orders of removal.” Jurisdictions that ignore immigration detainers would be responsible for “possible public safety risks,” the statement added.

García’s proposal is on the county board’s agenda for Wednesday morning. Possible steps by commissioners include referring the measure to committee or approving it immediately.