Trevor Hughes

USA TODAY

BOULDER, Colo. — County sheriffs who run America's jails are increasingly refusing to honor federal requests to detain suspected undocumented immigrants.

In most jails, incoming inmates are fingerprinted and run through a federal system to check their immigration status. The Department of Homeland Security then flags those suspected of being in the country illegally and issues a "detainer" — a form many sheriffs believed was equivalent to a warrant — to hold onto the person until Immigrations and Customs Enforcement can come get them for possible deportation.

But a series of court decisions has made it clear to sheriffs that the detainers are simply requests, and that holding onto people after they've finished their sentence or would otherwise be eligible to get bailed out violates the Constitution.

"I'm not taking a stand on immigration, but I'd like to point out that the system is really screwed up, and they're leaving us in a bad position. There needs to be a better way to do business," said Boulder County Sheriff Joe Pelle. "Everybody is being forced to have their county attorneys look at this … and change their policy."

Pelle in April joined several other Colorado sheriffs in announcing he would no longer honor the ICE requests. The detainers request that sheriffs hold a suspected undocumented immigrant for up to 48 hours beyond their normal release time. Add in weekends and holidays, and 48 hours can stretch to nearly a week, says Mark Silverstein of the Colorado ACLU. Boulder County saw about 150 ICE detainer requests in 2013, Pelle said, out of 10,000 bookings.

"Even 48 hours is a very long time to someone who should be free," Silverstein said. "The government has to have adequate grounds to deprive someone of their liberty. Even for a few minutes, it needs to be justified."

Thirty counties in Oregon changed their policies following a an April federal court decision that ruled Clackamas County violated the Fourth Amendment rights of a woman held on a detainer even though she was eligible to post bail. California's Sonoma County in early May became one of the most recent counties to require ICE agents to get a court warrant in order to hold onto suspected undocumented immigrants.

"We're saying to ICE 'go out and get some probable cause,'" said Sonoma County Assistant Sheriff Randall Walker. "We're just asking ICE to provide us with the information that courts have said we need."

In a statement, ICE officials said releasing suspected undocumented immigrants back into the community poses dangers, both to the public and to the agents, and committed to working with local sheriffs to deport the most dangerous undocumented immigrants.

"U.S. Immigration and Customs Enforcement will continue to work cooperatively with law enforcement partners throughout Colorado as the agency seeks to enforce its priorities by identifying and removing convicted criminals and others who are public safety threats," the agency said in a statement.

Cook County, home to Chicago, stopped honoring ICE detainer requests in late 2011. In the five months following that change, 346 people were released despite an ICE detainer request, and 11 went on to be re-arrested later on new charges, the Chicago Sun-Times reported. And in March, the Chicago Tribune reported that an undocumented immigrant, released because the local sheriff refused to honor an ICE detainer, was later charged with killing his ex-girlfriend.

Suspects in held in county jails on very serious charges, such as murder, aren't usually eligible to bond out, sheriff's said, regardless of their immigration status.

"In most cases where it's a serious violent felony, they wouldn't be getting out anyway," Walker said.