The Establishment Clause of the First Amendment restricts Congress with regards to public practice of religion.
The text of the clause reads:
|“||Congress shall make no law respecting an establishment of religion.||”|
As a result of this clause, enacted into the Constitution as a part of the Bill of Rights in 1791, Congress may not establish an official state religion, nor give preference to one religion over another. The original prohibition has been expanded by the Fourteenth Amendment to include not just Congress, but government organizations at the state and local levels. It does not apply to actions by private organizations, such as private schools; however, many states have enacted more restrictive measures, called collectively Blaine amendments, to prohibit State funding of sectarian schools.
The Establishment Clause is also complemented by the Free Exercise Clause which continues "or prohibiting the free exercise thereof." In addition to being restricted from favoring one religion over another, the government may not unduly restrict one religion over another or the practice of religion.
The Establishment Clause creates the basis for separation of church and state. A long series of court cases have been filed to determine how the Establishment Clause applies to specific fact patterns. In response to lawsuits asserting the Establishment Clause, courts have ruled against school prayer and public displays of the Ten Commandments on government property.