A wide variety of our laws are consistent with--and may have been enacted in part because of--religious beliefs.  Mere consistency with the religious beliefs of a legislative majority is not enough, of course, to render a law a violation of the Establishment Clause.  Were it otherwise, laws against murder or stealing would be constitutionally suspect because such acts were among those forbidden in the Ten Commandments.  Laws against murder and stealing obviously are supported by strong secular justifications in addition to any religious motivation behind them.  On the other hand, a law prohibiting the worship of any graven image, a violation of the Second Commandment, would clearly be a violation of the Establishment Clause because its predominant purpose and effect would be religious, not secular.
 

The difficult cases are those in which their was a strong religious purpose for enactment of a law or adoption of a governmental practice, but where the state can also assert some secular justification for the act in question.  McGowan v Maryland, considering the constitutionality of a state Sunday closing law, is such a case.  Clearly, the decision to require closing of certain commercial establishments on Sunday (rather than, say, Tuesday) had something to do with the Biblical admonition to "Remember the Sabbath and keep it holy."  But the Court found that the secular benefits of having a uniform day of rest, allowing the scheduling of community activities free from many work conflicts, predominated over any present day religious purposes or effects, and thus the Sunday closing law was constitutional.  The Eighth Circuit used a similar analysis in Clayton, upholding the Purdy, Missouri school district's ban on dancing, finding a secular purpose even when there was ample evidence that the no-dancing policy was maintained in response to pressure from conservative local church groups. 

In Marsh v Chambers, the Supreme Court considered the constiutionality of Nebraska's practice of beginning each day in its state legislature with a non-denominational prayer.  In an opinion relying to an unusual degree on framer's intent, the Court upheld the practice, reasoning that the same First Congress that proposed the Bill of Rights also voted to hire a congressional chaplain and begin its legislative days with a prayer, and therefore could not have intended in the Establishment Clause to have prohibited legislative prayers.  Given what the majority saw as clear framer's intent, the Court refused to apply the Lemon test usually used in Establishment Clause cases.

Larkin v Grendel's Den involved a challenged delegation of state legislative authority to churches.  Massachusetts law allowed churches (as well as schools) to veto liquor licenses for establishments within 500 feet of their building.  Voting 8 to 1, the Court struck down the Massachusetts law.  Suggesting that a flat ban on locating taverns within 500 feet of churches and schools might be constiutionally permissible, the Court saw danger in the possibility that churches might use their veto power to favor licenses for members of their own congregations.  The delegation of legislative power to churches was found to violate two prongs of the Lemon test, including the third (least often cited) prong: it excessively entwined religious groups in the processes of government.

Presbyterian Church v Hull Church (1969) can also be seen as a case of excessive entanglement, although at the time of the decision the Court was more inclined to see the state action as constituting a violation of the free exercise of religion.  In Presbyterian Church, a unanimous Court concluded that it violated the First Amendment for Georgia to apply a "departure-from-doctrine" test to determine whether a national church or local church was entitled to ownership of church property after the local church severed ties to the national church because of a theological dispute.  It was not appropriate, the Court said, for a jury or a reviewing court to try to determine which side in the dispute (involving such issues as ordination of women as ministers) strayed further from true Presbyterian teachings.  The dispute had to instead be decided using neutral principles of property law.