W hen the FBI took on the Mafia in the 1980s, agents were never short of leverage to use to recruit informants.

If a low-level Mafia soldier was popped for stealing a car, the FBI line was simple: Hey, would you rather work for us or go to prison?

After the 9/11 attacks, the FBI became the front-line agency in the war on terror. A presidential directive instructed the FBI to increase its ranks of informants, particularly in Muslim communities, where the bureau’s intelligence capacity was underwhelming.

But the FBI had a problem: It needed a recruiting strategy for Muslims. While agents could, and did, use criminal offenses by Muslims as leverage, as they had done against the Mafiosi, the bureau chose to widen its net in Muslim communities by looking past those with known links to criminal enterprises to individuals who simply wanted to remain in the United States. Many of these people have been targeted not because of anything they have done, but merely because the bureau sees them as potential sources of intelligence on other members of their communities.

If they have immigration problems, then that becomes a key pressure point. Potential Muslim recruits are offered a variation on the bureau’s line to mobsters: Hey, would you rather work for us or be deported?

The FBI’s Confidential Human Source Policy Guide — a nearly 200-page manual for how FBI agents should recruit and handle informants, classified secret and obtained by The Intercept — devotes an entire chapter to immigration, reflecting the outsized importance of leveraging a relatively vulnerable population of immigrants in recruiting informants. While the guide does not explicitly state that agents should exploit a potential informant’s immigration status, other government documents have come remarkably close — even using the phrase “immigration relief dangle” — and real-world examples of agents doing exactly this are plentiful.

In response to questions for this article about its use of immigration status to put pressure on potential recruits, the FBI maintained that the choice to become an informant was only ever a voluntary one.

Agents are prohibited from working with informants who do not have legal immigration status, according to the guidelines. As a result, agents are required to assist immigrants who lack legal status to obtain it before they can be enrolled as informants, and to this end, the bureau makes arrangements with Immigration and Customs Enforcement. In some instances, the FBI can help secure legal status or asylum for informants. But the guide makes clear that as often as not, the bureau avails its informants of temporary immigration relief. Once these informants are no longer of value to the bureau, agents are required to assist ICE in locating them. “If the [informant]’s location is unknown, the [FBI agent] must work with ICE to locate the individual,” the classified manual reads.

Asked whether such practices suggest that the FBI’s authority is blurring into immigration enforcement, the FBI replied: “FBI policy requires case agents to know the general location of confidential human sources, regardless of immigration status.”

This policy shows that the FBI is required to work much more closely with ICE than agents have previously suggested, said Ira J. Kurzban, a Miami-based immigration lawyer who has argued cases before the U.S. Supreme Court.

“In most cases, individuals will go to the FBI and the FBI will say, ‘Yeah, we don’t have any problem with you; you’re cleared,’ and yet ICE is aggressively going after them,” Kurzban said. “To the extent that this document reveals what’s really going on, it’s obvious that the FBI is working with ICE notwithstanding what they’re telling the individuals.”