Montgomery officials are getting a civics lesson in the power of the federal government: A controversial federal immigration enforcement program will launch in the county this fall, whether local officials like it or not.

In a terse letter, a U.S. Immigration and Customs Enforcement official told Montgomery’s corrections director that the program, called Secure Communities, is coming soon. As part of the program, fingerprint data from local law enforcement are sent to federal immigration officials.

“This letter is to notify you that the activation date for Montgomery County is scheduled for Tuesday, September 27, 2011,” the three-sentence letter said.

Montgomery already sends information to ICE about people arrested on charges of violent or gun crimes, regardless of whether they are immigrants. It also regularly sends a list of foreign-born inmates to immigration officials. County officials are concerned that the new program’s broader net will draw in many upstanding individuals or those who have made minor mistakes.

In Prince George’s County, for example, a large majority of undocumented immigrants deported via the program were not criminals. Advocates say they are concerned that some victims of domestic violence might stop calling police for help because they fear it will lead to their deportation.

At a rally outside the County Council building in Rockville on Tuesday, Florinda Lorenzo, an undocumented immigrant from Guatemala, described being arrested and jailed a year ago for selling phone cards from her home in Langley Park. Now she faces deportation and will voluntarily leave her three young children, all U.S.-born, with their father and move back to Guatemala to apply to immigrate legally. “I just don’t want to go. I want to stay with my kids right here,” she said.

The District is not participating in the program but will eventually do so, local and federal officials said. Arlington is part of the program — over the vigorous objections of local leaders who thought that their participation was voluntary. But local officials, including those in Montgomery, have learned that federal law trumps local preferences on immigration matters.

The ICE letter was written April 26, the same day council member Nancy Navarro (D-Eastern County) proposed a resolution saying the council “opposes implementation of the Secure Communities initiative in Montgomery County.”

By Tuesday, after scrambling to figure out where the county and council stood legally and politically, council members unanimously passed a radically overhauled version of Navarro’s resolution. The council, it declared, “encourages our public safety officials to work closely with ICE to ensure that the Secure Communities program is implemented consistent with its stated purpose and goals.”

“The resolution itself changed 180 degrees,” said council member George L. Leventhal (D-At Large).

Still, Navarro said, it’s important for the council to be on record with its deep misgivings.

“They’re saying, ‘We’re coming,’ ” Navarro said of immigration officials, adding it’s important for the council’s message to be heard as well. According to the resolution, the federal program, “as currently administered, will create division in our community, promote a culture of fear, and dismantle the trust that our police officers have worked to establish in many immigrant communities.”

ICE defends the program, which it said helped deport 72,445 undocumented immigrants with criminal backgrounds from October 2008 through March. Of those, 26,473 were found guilty of crimes as serious as murder, rape and the sexual abuse of children.

The program, which began in the George W. Bush administration and was greatly expanded by the Obama administration, sends the fingerprints of suspects picked up by local police to immigration officials. The fingerprint is checked against a national database of undocumented immigrants, and if there is a match showing that the person in custody is in the country illegally, federal officials ask the local police department to detain the suspect for an immigration check.

When the program was activated in any given area, ICE spokeswoman Barbara Gonzalez said, it tended to first identify “lower-level criminals as they are first to complete their criminal sentence and come into ICE custody.” But over time, she said the program usually identified an increasing number of undocumented immigrants with links to violent crimes and a decreasing number who had committed less-serious crimes.

After conducting their own investigations, immigration officials sometimes place detainees into deportation proceedings. Officials have said that the program prioritizes the removal of violent and dangerous criminals but that they are also required by law to remove non-criminal undocumented immigrants who come to their notice via the program, if sufficient detention and removal resources exist.

County Executive Isiah Leggett (D) said the county’s own notification system has worked well. “Unless there are some changes, it will supersede our local program,” Leggett said. While the county plans to continue expressing its disappointment and trying to work with federal officials, he said, “I’m not sure we will have any success on that. They’ve got a national program in place, and they’re just imposing it, whether you agree or not.”

Leggett spoke by phone from a White House meeting of county officials from across the country discussing local concerns, immigration enforcement among them. He said the homeland security secretary acknowledged shortcomings in the way the government has communicated to locals about the federal effort. “Janet Napolitano got up and said they miscommunicated to a lot to people in counties about Secure Communities,” Leggett said.