The Bill of Rights First Amendment:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press, or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
The Amendment's position on religion is more clear than some people care to recognize. The Establishment clause is pretty broad in that it refers to "no law" and the generic "religion". While there is no statement specifically calling for a "wall of separation" the language is clear that such a wall exists concerning laws. The verb "establish" per Merriam Webster:
Main Entry: es·tab·lish
Function: transitive verb
Etymology: Middle English establissen, from Anglo-French establiss-, stem of establir, from Latin stabilire, from stabilis stable
Date: 14th century
1: to institute (as a law) permanently by enactment or agreement
2obsolete : settle 7
3 a: to make firm or stable b: to introduce and cause to grow and multiply
4 a: to bring into existence : found
b: bring about , effect
5 a: to put on a firm basis : set up
b: to put into a favorable position c: to gain full recognition or acceptance of
6: to make (a church) a national or state institution
7: to put beyond doubt : prove
The definition is pretty clear, what isn't quite as clear is what is religious and what isn't when referring to law.
The sticking point is what law is about. One would take this on the surface as being pretty easy, defining what you cannot or can do under the force of the state. There is a huge "but" included in that. Is law about morality or is it about order? This dispute has been going on since, it seems, time immemorial. The stance of the religionists is that morality is the question. This view has a lot of precedence and has been practiced in the US - generally as complete failures. The huge rub is the idea that you can institute morality under threat of force. This is what law means, the state's view of a behavior is enforced, that is backed up by its full resources, including guns and bars. Once you get to the core of it you find that morality and law plainly are not congruent. In reality what law is about is social order.
Social order is a recognition that the disparity in human motivations result in behaviors that must be regulated in order for us to live in close proximity to each other. It is a fact that humans kill each other and the state has separated that behavior into categories from acceptable and approved to levels of disapproval. Soldiers are encouraged and trained to do so, people in general are discouraged. They are discouraged from doing so because unrestrained killing in a society leads to chaos because it leads to more killing. The state's interest in the morality of the act is disposed of by its sanction of it in its own interest, soldiers, and the levels of constraint including allowance for the citizenry. Killing ranks at the top of the morality scale concerns and yet the state does not disapprove in certain conditions. Morality is absolute, it certainly recognizes trade offs and conditions, but it is degrees of wrongness. Stealing to feed your family is still stealing and is still wrong, but a difference is seen in the motivation. For an example: a Catholic would still be required to confess this as a sin but the penalty the priest would apply would recognize the motivation. The law has no such quibble, the judge might consider it but is not legally induced to do so.
Here is where the crunch occurs, there are a lot of behaviors that religions or moral structures many people hold simply don't allow for. Two of the current big ones are homosexuality and abortion. These actions are disapproved of strenuously and vocally by a large number of voters. Homosexuality, where it regards consenting partners, is not much of a moral issue, it is primarily a religious and psychological question. If you take homosexuality as simply a behavior and remove all questions of religion and feelings from it, as a matter of social order it is immaterial. The question of love, sex, and gender is meaningless to social order, there are no economic or social impacts, beyond the issue of stability regarding homosexual marriage which is positive. The fact of homosexuality may bother people on an emotional level but it has existed as a matter of fact for all of recorded history. Being bothered on an emotional level may be annoying, but it scarcely rises to the level of law. It is a fact that many religions proscribe the practice and push to have their view enforced. It is the legal enforcement of a socially harmless activity that creates harm. It creates harm not only to government by putting it in a position counter to its mandate but also to the religion itself.
Backlash against the Mormon church for organizing millions of dollars and thousands of man hours of volunteerism to back California's Prop 8 is occurring within the Church. Outside the Mormon church people who have held no particular regard for it are finding themselves offended by their aggressive campaign. Being offended by Mormonism is no different than being offended by Lutheranism, silly behavior about a personal issue. It is entirely another issue to be offended by the actions of a religious organization, in this case Church of Latter Day Saints, and I am offended. I am offended enough that I will not purchase from a Mormon controlled corporation, such as Safeway. I don't care in the least about their views of homosexuality, I find that entirely their business, but I am outraged by their behavior within the legal sphere. It is an unacceptable legalization of their religious views and since legal punishment seems out of the question, economics becomes the tool. They need to be punished severely enough to dissuade them from going there again. Let me be very clear, this is about the Church not individual Mormons.
The issue of abortion is much more complex since it is not only a matter of religion and psychology, it is matter of a lives. Here there is a collision of religion, morality, ethics and social good that has explosive arguments scattered all through all of these. It is a simple matter to argue that it is a matter of reproductive freedom, but that argument taken fully would hold that at anytime previous to delivery an abortion is acceptable. This stance does not have any real support so the argument descends into arguments about the start of life, another logical dead end. Once a sperm has penetrated and egg and cell division has started life has begun, whether the body can take it forward or not. This is the crux of the explosiveness of the arguments, taken to their logical ends the results are counter to social order and sensibility and create huge uproars over procedures misnamed partial birth abortions or morning after pills. The Catholic Church disapproves and this leads to matters regarding Barack Obama like this:
"If you are one of the 54 percent of Catholics who voted for a pro-abortion candidate, you were clear on his position and you knew the gravity of the question, I urge you to go to confession before receiving communion. Don't risk losing your state of grace by receiving sacrilegiously," the Rev. Joseph Illo, pastor of St. Joseph's, wrote in a letter dated Nov. 21.
Political activity is punished within a religious organization and while this example concerns Catholicism it certainly is not limited to that. It is certainly acceptable religious behavior to proscribe an activity itself to its practitioners, it is another to proscribe a vote to allow others to engage in it. This stance is that the views of the Catholic Church must be applied to all and any dissent is punishable, an assumption of governmental powers by a church.
One cannot nor should expect that the religious views or moral construct of a person do not carry into the body of government with them. While it probably has little to do with their capacity to participate in governmental activities, it should do no more than inform their personal choices. The measure of political success for society involves the order of that society. It is important to note that certain aspects of societal order are removed from the government's hands, freedom of speech is a glaring example. This is also the case with the Establishment clause, the government is proscribed from such religion based behavior and that would include gay marriage or abortion. In each the measure should be its effect on social order and how best to deal with it - secular pragmatism.
The Establishment Clause makes it clear the the institution of religion through law is prohibited and religion is composed of its beliefs and tenets. The fact that a religion's tenets may comply with a law, theft for example, is not evidence that the law is based on that consideration. The fact of religious or moral proscription of theft does not affect the social order considerations, it may reflect religious dogma that it is a social order consideration. Secular pragmatism would ignore the religious and moral considerations of a law and attempt to order society in the least intrusive manner congruent with the success of that society.
It is very tricky business where something like abortion is concerned. The balancing act is extreme, abortions are going to happen with social costs incurred whether they are legal in some degree or not. The job of government in this case is to try to minimize the negative outcomes of the inevitable. No government is capable or qualified to legislate morality, there is entirely too much of its function that is not moral for it to do so. The government can certainly instruct in what is congruent with social order and take legal action to help encourage orderly behavior. Reliable and available birth control, applicable sex education and adoption support do more to lower abortion rates without governmental interference than all the confessions for a vote ever will.
Secular pragmatism would look at the social outcomes of gay marriage and measure the costs and benefits to society. Stable relationships and legal structures for inheritance and responsibilities are net gains whatever the sexual orientation of couples; the social order negatives involve the discomfort for some of Mr. & Mr. or Mrs. & Mrs. as titles. Confusion about the role of government in marriage does not exist when secular pragmatism is used, the state's view of marriage and the religious aspect are not congruent nor interfered with. The First Amendment bars the government from interfering in the "free expression" of religion, which obviously bars it from forcing religions to acknowledge gay marriage, or especially forcing them to perform one. Marriage is one of those issues where there is a similarity between government's interests and religion, but that similarity should not be confused with congruence. Government's interest is purely social order, divorced (if you will) from the religious aspects of marriage and the outcomes are not the same. The government allows divorces for rather simple reasons for social considerations, regardless of any religion's views of divorce.
Because government's aims are of an entire secular nature, it is dangerous for both institutions to become intimately involved with each other. It is impossible for the government to hand out money without attached strings - it is taxpayer money and responsibility is demanded. When religious tenets are legally instituted on the basis of that fact, religion is granted a place in government that it should not have and society is allowed to object, in very strong terms. This places the onus for law on religions, see Mormonism above. When the citizenry rightfully revolts from the institution of religious law the religious will be made to suffer. When religion usurps the function of government is will be made to pay the costs and success at that endeavor of instituting religious laws encourages further attempts which will elevate the level of resistance. Theocracy is incredibly dangerous for the members of religion, at some point they will be made to pay. JFK's Presidential endeavor was hampered by the assertions of Papal interference. Mitt Romney's chances for elective office votes with some segments of society that might have supported him before became nil with this activity. His religion has rightfully become a measure of his electability, simply because it is demonstrably officially an advocate of theocracy. Their business activities become targets for the same reason, if you object to theocracy then its advocates must pay.
The sad part of this is that it has become a measure of a religion's success to interfere in the secular behavior of the government. This very success undercuts its appeal where it needs to have it, within the community of the religious and others who are informed by religious thinking. It is indubitable that religions have had success within social thinking, churches were a large part of the Civil Rights campaign, but that success is undermined by the enforcement of their dogma. Enthusiastic atheists frequently point to the disasters of the influence of religion, particularly in governments. The problem for religions is that the arguments are good and compelling and speak to those who might become members otherwise. Those whose own behavior and sensibilities are congruent with a religion's find themselves confronted with that religion imposing those views and are offended, rather than joining.
The Framers of the Constitution and Bill of Rights understood that a line between government and religion was to the benefit of all concerned. Government functions better by staying in its actual role, religion is not interfered with, and the citizenry is free to choose as it will and finds it easier to obey laws with sense behind them.