three plastic animals rule
n.— «The Court held unconstitutional the nativity scene in Allegheny, which was tastefully displayed with a backdrop of greenery and poinsettias, but unaccompanied by secular signs of the season. Practitioners have dubbed the holdings in Lynch and Allegheny “the three-plastic animals rule.”» —by Geoffrey R. Stone Bill of Rights in the Modern State Oct. 15, 1992. (source: Double-Tongued Dictionary)