Former Vice President Walter Mondale and former Minnesota Supreme Court Chief Justice Kathleen Blatz have backed a lawyers group opposed to a proposed amendment which would define marriage as a heterosexual union in the Minnesota Constitution.

In a letter released Tuesday, Mondale and Blatz endorsed the efforts of Lawyers United for All Families.

“Our constitution is a hard-earned gift from those who preceded us, and an enduring promise to those who will follow us,” said Mondale. “It should be used to protect individual liberty, not to take it away.”

Added Blatz: “At this crossroads in Minnesota's history we must not allow our state's constitution to get caught up in the prevailing winds of the day. We may disagree on how best to recognize committed same-sex couples, but I believe quite firmly that legislating this issue by constitutional amendment is both inappropriate and a threat to the legacy of our state.”

Voters will decide on the issue during the November general election.

(Related: Catholics protest church's support for Minnesota's proposed gay marriage ban.)