U.S. District Judge Bernard Friedman will hear arguments Thursday in a case challenging the constitutionality of Michigan's 2004 voter-approved amendment limiting marriage to heterosexual unions.

At the suggestion of Friedman, April DeBoer and her partner Jayne Rowse of Hazel Park amended their lawsuit seeking to jointly adopt their three foster children to instead challenge the state's marriage ban.

“This is not the road we thought we'd go down,” Rowse, 48, told the Detroit Free Press. “We thought Judge Friedman would rule one way or the other on second-parent adoption. No one anticipated this. It was out of left field.”

“I know we're taking on a bigger issue with same-sex marriage,” DeBoer, 41, said.

Because they aren't married the couple cannot jointly adopt Nolan, 4, Jacob, 3, and Ryanee, 3.

“The state gave them children who had been abandoned and surrendered at birth to raise,” said lawyer Dana Nessel. “And they are raising them with all the love, nurturing, care and affection that any parent would give to any child. But the state then rewards these woman by telling them while they are good enough to foster as a couple, they aren't good enough to adopt as a couple. We submit that this is pure and utter insanity.”

Michigan attorney general's office has asked the court to dismiss the suit, saying there is no “fundamental right to same-sex marriage.”

In a court filing, the state argued: “Michigan's marriage amendment bears a reasonable relation to legitimate state interests. Michigan supports natural procreation and recognizes that children benefit from being raised by parents of each sex who can then serve as role models of the sexes both individually and together in matrimony. Plaintiffs fail to allege facts showing there is no rational basis for these legitimate state interests.”

There is no timeline on when Friedman will rule on the matter.