An American Civil Liberties Union lawyer will make history in December as the first openly transgender attorney to argue before the U.S. Supreme Court, opposing Tennessee’s Republican-backed law banning gender-affirming medical care for transgender minors.

The ACLU’s Chase Strangio, 41, represents a group of transgender people who pursued a lawsuit challenging the measure that prohibits medical treatments including hormones and surgeries for minors experiencing gender dysphoria.

ACLU Legal Director Cecillia Wang called Strangio the leading U.S. legal expert on transgender rights.

“He brings to the lectern not only brilliant constitutional lawyering, but also the tenacity and heart of a civil rights champion,” Wang said.