Question of Law or Fact?

Here is an interesting juxtaposition of articles.  In a trial in Michigan challenging the constitutionality of Michigan's state constitutional amendment barring same sex marriage, expert testimony has been elicited that same sex couples can be competent parents:

David Brodzinsky, an expert in adoption and foster care and a former Rutgers University professor, said there are no "discernible differences" in children who are raised by same-sex couples and youth raised by heterosexuals.

"It's not the gender of the parents that's the key. It's the quality of the parenting," said Brodzinsky, based in Oakland,Calif.

At about the same time, in a brief filed in the 10th Circuit Court of Appeals in a case where a US District Court judge struck down Oklahoma's same sex marriage ban, a legal argument was advanced claiming that same sex marriage is bad for children. 

"Marriage encourages mothers and fathers to remain together and care for the children born of their union," the group's 93-page filing said. Severing the link, it said, "would powerfully convey that marriage exists to advance adult desires rather than serving children's needs."

Citing a court opinion from 1888 — 19 years beforeOklahoma's statehood — Alliance said marriage "is the foundation of thefamily and of society, without which there would be neither civilization norprogress," and cited a 1978 ruling that said traditional marriage was"fundamental to the very existence and survival of the (human) race."

So, is the effect of same sex marriage on children a question of fact or of law? 

Michigan case:

Oklahoma case: