California’s top state appellate lawyer is poised to make his U.S. Supreme Court debut in just a few weeks in support of shielding hundreds of thousands of undocumented immigrants from deportation under the Obama-era program known as Deferred Action for Childhood Arrivals.

Solicitor General Michael Mongan is requesting to split 40 minutes with Gibson, Dunn & Crutcher’s Theodore Olson, who would argue for certain individual DACA recipients. Mongan would represent the interests of 20 states—including California, New York, Connecticut, Delaware and Pennsylvania—that are arguing against the Trump administration’s efforts to rescind the program.