In boarding school, Mr. Gorsuch participated in the informal debates, where he was routinely teased, accused of being “a conservative fascist.”

“Part of who we are is trying to be political without being partisan; principled but not ideological," said moderator John Carr.

Though the rallies were billed primarily as protests against the invitation to President Donald J. Trump, protesters also condemned the new U.S. administration’s travel ban against seven majority-Muslim countries.

"The fight will continue to go state by state. There's a strategy by proponents to get more states on board before they bring a case to the court."

Mr. Gorsuch, who attended the Jesuit-run Georgetown Preparatory School in Washington, appeals to conservatives because of his views on religious liberty and life issues.