"They were brought to the United States as young children," she told CNN's Chris Cuomo on "New Day." "We sued the Trump administration for repealing the policy because we contend that the administration violated the administrative procedures act and the due process clause of the Constitution. And we seek to vindicate those rights in the court."
Napolitano, who served under President Barack Obama, is now the president of the University of California system and said there are at least 4,000 undocumented students in the system, with the majority under the Deferred Action for Childhood Arrivals program, or DACA. She was in charge of DHS when DACA was established in 2012.
On Tuesday, a federal judge ordered the Trump administration to reveal internal deliberative documents that went into the decision to rescind the DACA program, a partial victory for groups challenging the rescission in a California federal court.
Judge William Alsup ordered the government turn over the records by October 27 and said it must appeal "very promptly" if it desires to do so.
The order comes as a product of several lawsuits that are being heard together in the Northern District of California, including Napolitano's, the state of California and local jurisdictions.
All have challenged the administration's right to end DACA, an Obama-era program that protected young undocumented immigrants brought to the US as children, without lengthier procedural steps, and have sued to block the sunset of the program.
Recipients with permits expiring by March 5 were allowed to renew, but the two-year protections will begin running out March 6.
The case is being heard on an expedited track due to the deadline, and DHS had submitted a record of documents regarding the administration's decision-making that only contained publicly released documents, including statements and letters.
"There is absolutely no data to support that DACA was somehow a magnet for illegal immigration," Napolitano said on CNN. "The numbers show that illegal immigration to the country is at its lowest in decades."
In September, the Trump administration announced the end of DACA, which protects nearly 800,000 people. The administration also announced a plan to continue renewing permits for anyone whose status expires in the next six months, giving Congress time to act before any currently protected individuals lose their ability to work, study and live without fear in the US.