Former Vice President Walter Mondale and former Minnesota Supreme Court Chief Justice Kathleen Blatz have been named co-chairs of a lawyers group opposed to Minnesota's proposed constitutional amendment which would define marriage as a heterosexual union.

Mondale and Blatz will speak at a Thursday fundraising reception for Lawyers United for All Families.

The reception, to be held at the Graves 601 Hotel in Minneapolis, will benefit Minnesotans United for All Families, the official campaign working to defeat the amendment in November.

“Our constitution is a hard-earned gift from those who preceded us, and an enduring promise to those who will follow us,” said Mondale in a statement. “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.”

(Related: Jon Stryker gives $325K to fight Minnesota gay marriage ban.)