Chicago family fighting to stop the deportation of veteran who served 2 tours in Afghanistan Miguel Perez, Jr., did two tours in Afghanistan. Now, he faces deportation.

 -- A lawyer is fighting to keep a U.S. Army veteran who served two tours of duty in Afghanistan from being deported to Mexico.

Army Private First Class Miguel Perez, Jr., 38, says he has been fighting deportation for roughly five years after mistakenly believing his service in the military made him a U.S. citizen by default. Perez, who was born in Mexico and moved to Chicago when he was 8, first came to the attention of U.S. Immigration and Customs Enforcement (ICE) while serving a prison sentence after pleading guilty to selling cocaine in 2008, according to his attorney, Christopher Bergin.

Last week, a judge ruled against Perez, who had filed a request for relief against deportation orders under the United Nations Convention against Torture on the grounds that his military background would make him vulnerable to attack from drug cartels in Mexico, Bergin said. He explained that drug cartels frequently seek to use people with military experience for their own ends.

Bergin has filed a motion to appeal the judge's ruling, buying about a month of time for his client, who is currently in the custody of ICE, before the appeal is reviewed, he said.

In July 2002, President George W. Bush signed an executive order clearing the way for noncitizens who had served in the Armed Forces on or after Sept. 11, 2001, to immediately file for expedited citizenship. Perez's mother, Esperanza Medina, told ABC News her son never formally filed for citizenship because he misunderstood the rules.

"[The decision] is not fair to us because my son fought for this country," Medina, 60, who became a U.S. citizen in 2005, said of the judge's ruling. "He has a nation and it's the USA."

ABC News reached out to ICE regarding the most recent developments surrounding Perez's case and was referred to the Executive Office for Immigration Review (EOIR). EOIR did not immediately return a request for comment.

A spokesperson for ICE released a statement to ABC-owned station affiliate WLS in Chicago this past December regarding Perez's case, saying the agency "respects the service and sacrifice of those in military service, and is very deliberate in its review of cases involving U.S. military veterans."

"Miguel Angel Perez-Montes, 38, from Mexico, was convicted in February 2010 in Cook County, Illinois, for manufacture/delivery of more than two pounds of cocaine and sentenced to serve 15 years in the Illinois Department of Corrections. He was encountered by ICE while serving his prison sentence and placed into removal proceedings in 2012," the statement said. "On Sept. 23, 2016, Perez-Montes was turned over to ICE custody from the Hill Correctional Center in Galesburg, Illinois. He will remain in ICE custody while his removal proceedings are pending in federal immigration court."

The next steps Bergin is plotting for his client, beyond the appeal, will likely involve Illinois Sen. Tammy Duckworth, whom he is asking to take his client's case to Washington, D.C.

Bergin is hoping that Duckworth will use her political clout to get U.S. Citizenship and Immigration Services (USCIS) to backdate Perez's recent application for citizenship filed by his lawyer to an earlier date -- starting on the day he first served his country in the Army.

ABC News reached out to the Illinois branch of USCIS for a comment on whether this would be possible but did not immediately receive a response.

Duckworth, Bergin hopes, will see aspects of herself in Perez: She was born in Thailand and has served in the Army Reserve and Army National Guard.

ABC News reached out to Sen. Duckworth's office for a comment about Perez's case but did not immediately receive a response.

Bergin and Perez's family attribute his conviction to a period when Perez was self-medicating for pain related to his time in the service, they said.

Bergin added that Perez "was blown out of his Jeep in Kandahar," and that he suffered a traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) as a result of the blast. Perez told The Chicago Tribune last month that grenade and roadside bomb explosions during his tours led him to lose much of his hearing and suffer headaches.

After returning home from Afghanistan, Perez told the Tribune he longed for the adrenaline rush from combat and eventually turned to cocaine. He ultimately opted for an early discharge from the Army after failing a drug test, he told the Tribune.

Sara Walker, who works at Perez's family's church, Lincoln United Methodist Church in Chicago, told ABC News that Perez told her he turned to drugs for relief. Lincoln United Methodist Church helped connect Perez's family to Bergin, who is handling the case pro bono.

"He told me that when he made that mistake he was drinking and doing drugs 24/7," Walker said.