More than 60 groups have expressed opposition to same-sex marriage in a brief to the US Supreme Court, ahead of a hearing on 28 April.
Most of the submissions in the brief are from religious organisations, including the Southern Baptist Convention.
It warns that opponents of same-sex marriage have been silenced in the past and argues legalisation would lead to “additional violations of free speech rights”.
The groups that have written to the Supreme Court include Baptist, Lutheran and Methodist organisations, who say that redefining marriage will lead to conflict between the state and the church.
One group argues that Christians face being marginalised if they uphold a Biblical definition of marriage.
The Supreme Court is expected to make a decision by June this year on whether or not there is a constitutional right to same-sex marriage.
Free speech ‘violated
Individual states have been free to decide the issue for themselves but pressure on the courts from gay activists has resulted in many pro-traditional marriage votes being overruled.
Sixteen states, including Kentucky, Michigan, Ohio and Tennessee have called for existing bans on same-sex marriage to be upheld.
The brief states: “Unfortunately, in their zeal to advance and affirm same-sex marriage, many state actors have ignored or violated the very free speech principles that facilitated free and open dialogue on this once-settled question.
“As a cautionary tale of a road to potential tyranny, this brief details many incidents — personal and systemic; domestic and foreign — where religious dissenters from same-sex marriage have been silenced by state actors”.
It says that: “A decision from this Court imposing same-sex marriage nationwide would inevitably exacerbate these conflicts, and inexorably result in additional violations of free speech rights.”
“In reaching its decision”, it states that the Court should reaffirm that the US Constitution protects, “religious dissenters who disagree with state recognized same-sex marriage and to reaffirm the importance of free debate and free inquiry”.