She served as a law clerk to Judge Harry T. Edwards of the United States Court of Appeals for the District of Columbia Circuit, from 1990 to 1991.

From 1996 to 1999, she was an associate professor at the University of Pennsylvania Law School, earning the Harvey Levin Memorial Teaching Award.

She previously served as the Principal Deputy Assistant Attorney General of the Office of Legal Policy at the United States Department of Justice.

In 2009, she was named the Executive Director of the Supreme Court Institute at Georgetown, serving in that position until 2010, when she joined the Office of Legal Policy.

[8] Harris, who was joined by Circuit Judge Paul V. Niemeyer, held that religious schools have a constitutional right to select their own "ministers" who adhere to Catholic teachings.