Philadelphia District Attorney Larry Krasner could not have known that defending protestors arrested during the 2000 Republican National Convention would lead, nearly 18 years later, to the creation of a groundbreaking position within his office.

Yet Krasner, just weeks into his new role, stood next to one of those people Thursday morning as he introduced Caleb U. Arnold, the city’s inaugural immigration counsel.

The position, based on a similar role already in place in Brooklyn, will work as a liaison between immigrant communities and the criminal justice system. Arnold, who uses the pronouns “they” and “them,” will advise prosecutors on minimizing the impact of criminal convictions on their immigration status, especially for low-level offenders.

“Together, we will ensure that all people are treated fairly by the justice system regardless of their immigration status,” Krasner said. “This is also part of our overall effort to protect the most vulnerable and ensure they are able participate as witnesses or complainants in the criminal justice system.”

Arnold has more than 10 years experience litigating and representing immigration cases. But like so many of Krasner’s previous clients, they started as an activist first in their native Colorado and more recently in Philadelphia and New York.

The West Philadelphia resident first met Krasner as a young law student. Arnold, in town for the RNC, was arrested for protesting the death penalty outside the RNC. Krasner represented them, and several hundred others, in court. But he was impressed with Arnold’s passion and with their shared ideals, he told NBC10.

“I got to know Caleb both in their capacity as a defendant who won their case, but also in Caleb’s capacity as someone who was helping get others together,” he said.

Arnold will focus on ensuring that Immigration and Customs Enforcement officials do not use the courts as a “trap” to find and deport undocumented immigrants during criminal proceedings. This will include helping prosecutors secure visas for people who are cooperating with ongoing investigations.

“It is not fair to punish someone based on their immigration status,” Arnold said. “When people can come forward, we are more effective.”

Both Krasner and Arnold said their office’s protection will extend to people accused of low-level and non-violent crimes. The idea is to encourage a better relationship between law enforcement and immigrant communities by encouraging victims of crime to speak out and by not marginalizing already shunned residents.

Arnold’s appointment signals a new phase in Philadelphia’s ongoing battle with the White House. Philadelphia Mayor Jim Kenney has been vocal against President Donald Trump’s position on immigration. On Wednesday, Kenney tweeted that he had “no interest in going to the White House when the resident welcomes white supremacists and vilifies immigrants.”

Similarly, Krasner called Trump’s policies “misguided.”

“We are talking about having a criminal justice system that functions,” Krasner said. “Nothing we’re doing here makes it impossible for the feds to do what they need to do.”