The Canadian Supreme Court heard opening arguments Wednesday in a case seeking to legalize same-sex “marriage” across the country.

Opponents of the bill said allowing same-sex “marriages” could harm religions and the institution of marriage. They include the Attorney General of Alberta, the Canadian Council of Catholic Bishops, and a conservative women's group, REAL Women of Canada.

Robert Leurer, arguing on behalf Alberta, said the federal government cannot simply change the constitutional definition of marriage to allow same-sex unions, reported the Canadian Press.

David Brown, who represented a coalition of conservative family groups, said the rights of religious groups are in danger if the legislation passes.

"If the definition of marriage is changed and constitutionalized as to include same-sex marriage it will be open season on religious institutions," he said.

Church groups, including the Evangelical Fellowship of Canada, have repeatedly expressed concerns that legalizing same-sex “marriage” would force clergy and religious institutions to sanctify the marriages against their religious beliefs.

The bill which was referred to the country’s Supreme Court by former prime minister Jean Chretien last year questions whether the bill is within federal jurisdiction, whether same-sex marriage is consistent with the Charter of Rights and whether the charter protects the clergy from having to perform marriages against their religious beliefs.

Supporters of the same-sex “marriage” legislation include the Attorney General of Canada, the Canadian Human Rights Commission, various gay rights groups, the United Church of Canada representing Presbyterian and Methodist congregations, and a coalition of liberal rabbis.

The Canadian Supreme Court will hold two more days of hearings and expected to make a decision next year.