The Department of Homeland Security issued the advisory, which informs agents in the Tucson, Ariz., sector that they have three options if they encounter suspected drunk drivers -- detain them at the request of local law enforcement, detain them without the involvement of another agency or let them go.
In stark terms, the bulletin explains which options put the officers at greatest risk of being sued. The bulletin warns the first option poses the "greatest threat" to an agent of a lawsuit.
Instead, the advisory, obtained by conservative watchdog group Judicial Watch, highlights the third option – letting them "go on their way." The advisory makes clear agents have no legal obligation to intervene in state crimes and that with the third option, "there is generally no liability that will attach to the agent or agency for failing to act in this situation."
The bulletin, reviewed by FoxNews.com, goes so far as to say agents wouldn't be liable if they allow the driver "to continue down the road and they kill someone."
Jessica Vaughan, a policy director for the Center for Immigration Studies, said Tuesday the advisory is consistent with the administration's long-held strategy of trying to end federal agents' close cooperation with state and local law enforcement, which has led to deportations.
Vaughan argues that most border communities are so rural and have so few resources that local and federal officers must share responsibilities -- a practice known as "comity" in legal circles.
"That's the reality on the ground," she told FoxNews.com. "But the administration thinks Border Patrol agents have too much discretion, and it wants to draw a bright line between federal and other agents."
The leader of the union representing the majority of Tucson sector agents suggested they will continue to detain those suspected of drunken driving, despite the memo.
"I can assure you that the agents I represent and the people I work with just would not release someone who was severely intoxicated," Art Del Cueto, president of Local 2544, told a local CBS TV station.
He also said agents were devastated after a drunken driver struck and killed a coworker in 2010 near the Casa Grande part of the sector.
"We were hit hard by the death of one of our own," he said. "How could we release them?"
The debate comes as the Obama administration looks to move forward with a set of immigration actions that would expand the categories of illegal immigrants allowed to skirt deportation and seek work permits. A federal judge on Monday blocked those actions, though the administration plans to appeal. For years, though, the administration has tried to prioritize enforcement, telling agents to detain – and deport – high-level offenders while letting others get a pass. Officials have said it's a matter of resources.
Lawmakers and others intent on reforming U.S. immigration law almost uniformly agree the first step is to fortify the U.S.-Mexico border, and that Border Patrol agents are over-burdened.
A July 2014 inspector general's reports appears to bolster the argument, showing a CBP staffing analysis that called for an additional 3,811 agents.
Further, the Department of Homeland Security touts the Tucson sector as one of the agency's busiest -- reporting 87,915 apprehensions in fiscal 2014 along the 262-mile stretch.
However, there appears to be little public support for agents turning their backs on intoxicated drivers.
Judicial Watch President Tom Fitton on Tuesday accused the Obama administration of putting politics over public safety.
"Families across America are now at risk on the roads, as President Obama and his appointees at the Department of Homeland Security have given illegal aliens a license to drive drunk," he said.
The group Mothers Against Drunk Driving also responded to the advisory.
"MADD urges all law enforcement officers to protect the public by following standard procedures when encountering anyone suspected of driving under the influence of alcohol or drugs," group President Colleen Sheehey-Church said. "Law enforcement is the first line of defense in preventing drunk and drugged driving, and their efforts are crucial to keep our roadways safe."
The department advisory makes clear that its intent is to tell agents about their legal options when encountering drivers who appear to be impaired -- "not direct (them) to detain or not detain these drivers."
In addition, the advisory says that the information in the memo is "based on judicial precedent" and that agents are trained to exercise their professional judgment when encountering a suspected drunken driver.