The city of Boston violated the free speech rights of a religious organization when it refused to fly the group’s Christian-themed flag on a City Hall pole, a unanimous U.S. Supreme Court ruled on Monday.

“When a government does not speak for itself, it may not exclude speech based on ‘religious viewpoint’; doing so ‘constitutes impermissible viewpoint discrimination,’” Justice Stephen Breyer wrote for the court. “Here, Boston concedes that it denied (Harold) Shurtleff ’s request solely because the Christian flag he asked to raise ‘promoted a specific religion.’ Under our precedents, and in view of our government-speech holding here, that refusal discriminated based on religious viewpoint and violated the Free Speech Clause.”