 In 1985 , the United States Supreme Court ruled in ACLU v. Scarsdale , New York that nativity scenes on public lands violate separation of church and state statutes unless they comply with " The Reindeer Rule " — a regulation calling for equal opportunity for non @-@ religious symbols , such as reindeer . This principle was further clarified in 1989 , when the Supreme Court in County of Allegheny v. ACLU ruled that a crèche placed on the grand staircase of the Allegheny County Courthouse in Pittsburgh , PA violated the Establishment Clause , because the " principal or primary effect " of the display was to advance religion . 
