Janet Napolitano Tucker Higgins | CNBC

Janet Napolitano used to set records for the number of people she deported from the United States in a single year, angering immigrant-rights groups. In her new role, the former Homeland Security secretary under President Barack Obama has those groups on her side. Next month, Napolitano will head to war against President Donald Trump in a blockbuster fight at the Supreme Court that will impact the lives of millions of immigrants and their family members. The court fight is over the Deferred Action for Childhood Arrivals program, which shields about 700,000 young people who were brought to the country unlawfully from deportation and allows them to receive work permits. "The real question is who is being deported," Napolitano said in a recent interview in Manhattan, explaining her position as a tough-on-the-border advocate for immigrants. Napolitano was instrumental in establishing the DACA program, which she signed into action in 2012 as DHS secretary. Now, she is leading the legal challenge to the Trump administration's efforts to end it. Napolitano is acting in her capacity as the president of the University of California system, the academic home to more than 1,000 DACA recipients. "I saw [DACA] first from the vantage point of being the Cabinet official responsible for immigration and immigration policy," Napolitano said. "To then seeing the benefits the program created. To now, being at the university, where we have all of these DACA recipients as part of the university community." Napolitano said that when the Trump administration attempted to end the program in 2017, "we immediately went into high gear." "The next logical step was to file a lawsuit, which is what we did," she said. Since then, courts in Washington, California and New York have temporarily halted the Trump administration's attempts to end the program. The Supreme Court will hear arguments Nov. 12, and a decision is expected by the end of June.

Napolitano's mixed record

Homeland Security Secretary Janet Napolitano speaks during a ceremony honoring Senate Homeland Security and Governmental Affairs Committee Chairman Sen. Joseph Leiberman (I-CT) at the at the U.S. Citizenship and Immigration Services December 19, 2012 in Washington, DC. Chip Somodevilla | Getty Images

The situation has further muddied the waters around Napolitano's record, which were far from clear at the start. In addition to criticizing her role overseeing an escalation in deportations, immigration advocates have questioned Napolitano for not being tough enough on Sheriff Joe Arpaio in Arizona while she was U.S. attorney in the state, and for her role in expanding a program that enlisted local authorities in immigration enforcement. In early 2013, ABC News analyzed Napolitano's record in the Obama administration under the headline: "Janet Napolitano: Immigration Hero or Villain?" Months later, a UC alumus who is an undocumented immigrant wrote a stinging dissent against Napolitano's nomination to lead the institution. It was under that cloud that Napolitano eventually built out a vast legal support system for young immigrants when she took over the university system. And, with a year to go before she has said she will step down, she has put herself at the center of the fight for the young immigrants known as "Dreamers." "Let's just say it's complicated," said Frank Sharry, executive director of America's Voice, an immigrant rights group that was active during the original fight for DACA. Sharry said that on one hand, Napolitano does deserve credit for the work that she has done in California. On the other, he said, she's the reason why Obama came to be known as the "deporter-in-chief." "I know advocates who still spit bullets at her," he said. "People who lost family members to deportation are not very sympathetic to Janet Napolitano." The controversy over Obama's deportation record exploded out of immigration circles and onto the national stage recently, when former Vice President Joe Biden was pressed on his role in the deportations during the September Democratic debate. Biden prompted further scrutiny by claiming the administration "didn't separate families," despite the fact that it did sometimes do so. For her part, Napolitano defends herself against progressive critiques by deploying the same argument she's put forward in her legal challenge to the Trump administration: Border control is about setting priorities, and her top priority is deporting criminals, not children. "I think we had the right priorities and were enforcing the right priorities, and I think the approach of this administration, that anybody is fair game, is not good policy and it's not consistent with our values," Napolitano said. "In my view, the right approach is to recognize that we don't have the resources to deport all of them. It would be like deporting all of Los Angeles." Immigrant rights groups say Napolitano did not do enough to avoid deporting innocent immigrants. More than half of the more than 419,000 people deported in fiscal year 2012, for instance, were not criminals, according to the Pew Research Center. Napolitano says she got the ball rolling by the time she left the DHS in 2013. By 2016, more than 90% of those deported were convicted of serious crimes, she points out. Napolitano, a lawyer who has served as governor and attorney general of Arizona, is just as comfortable explaining her case against the Trump administration in legal terms as she is as a matter of policy. Legally, Napolitano said, refraining from deporting young, law-abiding immigrants is similar to the Justice Department's general reluctance to bring cases against those who pass bad checks. "That's just a realization that no law enforcement organization has the resources to do everything," she said. "And that's why law enforcement organizations have what's called prosecutorial discretion. And that's well embedded in the law, and it's the theory on which we built DACA."

The fight over DACA

In the Supreme Court's hands