As state recognition of same-sex marriage spreads,  awareness is rising about the threat it poses to religious liberty.

On Wednesday, the governor of Maine signed a bill creating government recognition of same-sex relationships. Lawmakers in New Hampshire have also moved forward on legislation that would redefine marriage, though it is not certain whether the governor of that state will sign the proposed law.

In April, the Iowa Supreme Court ruled that defining marriage as a relationship between a man and a woman is impermissible discrimination under the Iowa Constitution. This decision struck down the Defense of Marriage Act that Iowa lawmakers passed by large margins in 1998.

A few days after the Iowa decision, lawmakers in Vermont overrode a gubernatorial veto to enact legislation creating same-sex marriage in that state. A 1999 Vermont Supreme Court decision already had forced lawmakers to extend most of the benefits of civil marriage to same-sex couples. Lawmakers originally complied with that judicial mandate by creating civil unions; under the more recent legislation same-sex unions will be licensed as “marriages.”

In addition, the District of Columbia Council recently voted to recognize same-sex marriages performed in other jurisdictions. Before the legislation can become law, it must be reviewed by both the D.C. Mayor and the U.S. Congress.

Former D.C. Mayor Marion Barry was the only council member to oppose the D.C. legislation. One of the supporters of the legislation, council member David A. Cantania, reportedly described Barry’s position as “bigoted.”

Cantania’s public condemnation of support for marriage as a man and woman as “bigoted” reinforces serious concerns about conflicts between same-sex marriage and religious liberty. Arguments for same-sex marriage often assert that limiting marriage to relationships between one man and one woman is a form of irrational prejudice and unacceptable discrimination. But the understanding that marriage is a relationship between one man and one woman is a core religious belief for a significant number of Americans. Once government officials come to regard the traditional understanding of marriage as a form of irrational prejudice that should be purged from public life, religious individuals and institutions will face growing burdens on their freedom to express their beliefs about marriage, family, and sexual values.

However, lawmakers are beginning to recognize that same-sex marriage will burden religious liberty. In Connecticut and Vermont, for example, lawmakers recently enacted specific legislative protections for religious institutions that believe marriage is a relationship between one man and one woman.

The protections make clear, for example, that churches will not have to perform same-sex marriage ceremonies or rent facilities for same-sex marriage celebrations. These protections will not solve all the religious liberty problems associated with marriage redefinition. Nevertheless, though significantly limited in proportion to the scope of the problem, these protections demonstrate a growing awareness that same-sex marriage poses genuine threats to religious liberty.

Thomas Messner is a visiting fellow at The Heritage Foundation.