Former solicitors general Paul Clement and Donald Verrilli went head to head Monday in oral arguments at the U.S. Court of Appeals for the D.C. Circuit in a case that considers whether the Washington, D.C., public transit system’s refusal to run a religious advertisement is a First Amendment violation.

Kirkland & Ellis’ Clement represents the Archdiocese of Washington, which alleges a district court judge erred last year by refusing to grant a preliminary injunction requiring Washington Metropolitan Area Transit Authority to run the church’s Advent advertisements on city buses, which encouraged charitable giving during the winter Advent season. Though the Advent season has passed, the church wants to run the advertisement this year, too.