Thomas Kohler, professor at Boston College Law School
It depends upon the religious group. The teachings of those religious groups with disciplined bodies of doctrine, Orthodox Jews or Catholics for example, will not be affected. That is not to say that the external law will not influence the views of the adherents themselves, particularly those who are not especially well educated in the teachings of their faith.

The real impact of changes in marriage law will not be on their teachings, but on the religious institutions themselves. The external law will not, and under present First Amendment doctrine could not, force a religious group to conduct same-sex marriages if doing so would be contrary to their teachings. However, the law would require those religious groups to recognize such marriages, to grant spousal benefits to same-sex couples in employment situations, etc.

The California Supreme Court's recent opinion in Catholic Charities of Sacramento v. Superior Court, foreshadows the future. In that case, Catholic Charities was required to cover the cost of prescription contraceptives despite the Church's opposition to the use of contraceptives on religious grounds. Institutions sponsored by religious groups, such as schools and universities, charitable undertakings, and the like would be required, despite their own teachings, to recognize same-sex relationships and treat them no differently than heterosexual marriages. The ability of such groups to obtain broadcasting licenses and other privileges granted by the government would be affected. The impact of the law would be to push dissenting religious groups to the very edges of the society.

Andrew Koppelman, professor of law and political science at Northwestern University
The U.S. Constitution's guarantee of religious freedom means that government may not tell any religious group what to believe or what rituals to perform, and that includes decisions about what marriages ought to be celebrated. No state has ever attempted to compel the Catholic church to marry divorced persons whose former spouses are still living, or Orthodox Jewish rabbis to celebrate marriages between Jews and Gentiles. If any state ever tried, the First Amendment would protect these religious groups. So recognizing same-sex marriage would not require any religious group to celebrate such marriages. On the other hand, when culture changes, religion tends to follow. It was popular pressure, not the law, that induced Bob Jones University to abandon its rules against interracial dating. If the refusal to allow gays to marry comes to be regarded as merely the manifestation of lazy prejudice, then increasing numbers of people will be persuaded that the religious basis for that refusal is no better. And that will eventually change what religious groups teach.

Dwight Duncan, associate professor of law at Southern New England School of Law
At one level, they don't. Religious groups will still be able to marry whatever couples they want for the time being, with or without government recognition. But if we look at the effects that would ensue if recognition of homosexual relationships as "marriages" is legally mandated, then churches may be forced to "retreat from their practices, or else face enormous legal pressure to change their views," according to an opinion letter I signed with other constitutional law professors in March of 2004 regarding the looming Massachusetts situation.

In Canada, for example, a bill is pending in Parliament that would add "sexual orientation" to the hate propaganda law. According to John Leo of U.S. News and World Report, it is referred to as the "Bible as Hate Literature" bill, and would arguably ban public expression of opposition to gay marriage. Loss of tax-exempt status, academic accreditation, and media licenses could all ensue for religious organizations opposed to homosexual practices and gay marriage.

Brad Sears, executive director of the Williams Project on Sexual Orientation Law at UCLA
I don't think they have much impact, and that's a good thing. Religious groups should be allowed to have whatever rules their religions dictate for recognizing marriages. No religion should be required to recognize same-sex marriage.

However, many religions are far ahead of state and federal governments in recognizing same-sex marriages. Conversely, state and federal governments should not rely on religious definitions of marriage at all. Civil marriage should not be entangled with any religious beliefs or practices, and should be open to all on an equal basis. This is what separation of church and state is all about.

Peter Sprigg, director of marriage and family studies at the Family Research Council
It is important that all religious groups have complete freedom to practice their religion without interference by the government. This includes the right to hold whatever types of ceremonies and rituals they desire (without demanding recognition from the government); and it also includes the right to refuse to carry out ceremonies, including marriages (even when those unions may be legal under civil law).

Churches and other religious groups that are affirming of homosexuality have already been fully exercising these rights by carrying out ceremonies to celebrate the "union" of homosexual couples, even though such unions are not recognized by law as "marriages" anywhere in the United States. One would hope that that if homosexual couples at some future point are allowed to enter into legal civil marriages, just as much respect for religious liberty will be shown to churches and synagogues that refuse to conduct same-sex "marriages." In other countries, the adoption of homosexual civil marriage has not led directly to churches being punished for refusing to "marry" same-sex couples.

However, the growing official affirmation of homosexuality (of which homosexual "marriage" is only one symptom) has led to "hate crime" laws which have been used to punish religious believers even for the peaceful expression of their sincere opposition, on moral and religious grounds, to the practice of homosexuality.

Therefore, it appears that opponents of homosexuality have more to fear regarding the loss of religious liberty than do supporters of it, as this debate plays out in the future.

Gary Buseck, legal director at the gay rights group Lambda Legal
There is a clear distinction between the religious rite of marriage and state-sanctioned civil marriage. The state's decision to allow same-sex couples to marry could never affect or change each religion's choices as to whom it will marry and on what terms.

For example, the Roman Catholic Church will not marry a person who has been previously married and divorced. The fact that that person may divorce and remarry civilly does not, and cannot, affect the Roman Catholic Church's actions in any way. Similarly, when the government allows same-sex couples to marry, no church could ever be required to sanction such a marriage unless it chose to do so.

Of course, a number of religious denominations have for many years celebrated gay and lesbian marriages; and marriage equality for gay couples has had tremendous support from members of the clergy. At a town hall meeting that Lambda Legal held in northern New Jersey this spring nearly a hundred clergy members spoke of their support for our efforts to win the right to marry for gay and lesbian couples in that state. Many people of faith are behind our efforts.