“This is a failed state,” Mr. Contreras said. “The government can’t follow through on anything.”

Federal officials have rejected that assessment, noting that additional troops have quieted violence in some areas. But here in a part of the country that security experts now describe as Mexico’s toughest battleground in its war on organized crime, entire families have been turning to Mr. Contreras for a way out.

One resident, Amparo Zavala, 56, collected her letter from him after paying about $4. Hoping for asylum, she then traveled to Tijuana with her two grown daughters, a niece, her son and his wife. A bullet had already pierced the tin walls of her two-room home; she said she feared the next gunfight would lead to death.

But the American response was not what she expected. One of Ms. Zavala’s daughters was born mentally disabled, and, she said, at the port of entry in the San Ysidro district in California, agents pulled them apart. “Please, please, she needs me!” Ms. Zavala recalled screaming. That night was the first time she and her disabled 35-year-old daughter slept apart.

Two weeks later, after being sent to Arizona, Ms. Zavala said she was deported with a five-year ban on re-entering the United States. Her daughter-in-law was also deported, but the others remained, a decision Ms. Zavala still does not understand. “The letter was for all of us,” she said. “We were all telling the truth.”

Many other families described similar situations. Just a few blocks away, closer to the town plaza, Isamar Gonzalez described her own confusion about why her mother could stay in California for a court date more than a year away while she was rejected. “My mother has diabetes,” she said. “Maybe that’s it?” Probably not, Ms. Zavala added: “I have diabetes, too.”

Homeland Security officials emphasize that the asylum process has always been complicated, with officers scrutinizing a range of evidence to determine whether applicants meet the legal standard of a “credible fear,” which typically allows them to stay in the country freely while their asylum case proceeds to a judge. There are also safeguards and background checks, Homeland Security officials said, to keep out the criminals and fraud that Mr. Goodlatte has said are becoming a bigger part of the system.

Image With letters from La Ruana, many go north from Tijuana. Credit... The New York Times

“Credible fear determinations are dictated by longstanding statute, not an issuance of discretion,” said Peter Boogaard, a Homeland Security spokesman.