In "Engel v. Vitale" (1962) the Court ruled that government-imposed nondenominational prayer in public school was unconstitutional. In "Lee v. Weisman" (1992), the Court ruled prayer established by a school principal at a middle school graduation was also unconstitutional, and in "Santa Fe Independent School Dist. v. Doe" (2000) it ruled that school officials may not directly impose student-led prayer during high school football games nor establish an official student election process for the purpose of indirectly establishing such prayer. The distinction between force of government and individual liberty is the cornerstone of such cases. Each case restricts acts by government designed to establish prayer while explicitly or implicitly affirming students' individual freedom to pray.