The First Amendment's Establishment Clause prohibits the government from making any law “respecting an establishment of religion.” This clause not only forbids the government from establishing an official religion, but also prohibits government actions that unduly favor one religion over another. It also prohibits the government from unduly preferring religion over non-religion, or non-religion over religion.
Although some government action implicating religion is permissible, and indeed unavoidable, it is not clear just how much the Establishment Clause tolerates. In the past, the Supreme Court has permitted religious invocations to open legislative session, public funds to be used for private religious school bussing and textbooks, and university funds to be used to print and publish student religious groups' publications. Conversely, the Court has ruled against some overtly religious displays at courthouses, state funding supplementing teacher salaries at religious schools, and some overly religious holiday decorations on public land.
One point of contention regarding the Establishment Clause is how to frame government actions that implicate religion. Framing questions often arise in the context of permanent religious monuments on public land. Although it is reasonably clear that cities cannot install new religious monuments, there is fierce debate over whether existing monuments should be removed. When the Supreme Court recently considered this issue in Van Orden v. Perry, 545 U.S. 677 (2005), and McCreary County v. ACLU, 545 U.S. 844 (2005), it did not articulate a clear general standard for deciding these types of cases. The Court revisited this issue in Salazar v. Buono (08-472), a case which considered the constitutionality of a large white Christian cross erected by members of the Veterans of Foreign Wars on federal land in the Mojave Desert. While five justices concluded that a federal judge erred in barring a congressionally ordered land transfer which would place the memorial on private land, there was no majority reasoning as to why. Three Justices held that the goal of avoiding governmental endorsement of religion does not require the destruction of religious symbols in the private realm, while Justice Scalia and Justice Thomas concluded that the plaintiff lacked standing to bring this complaint.