There are a number of significant aspects of the court's opinion. First, the court relied upon the New Mexico Constitution, not the United States Constitution. That means that this decision cannot be appealed to the United States Supreme Court. The New Mexico Supreme Court has the final say regarding the meaning of the New Mexico Constitution.
Second, the court concluded that the appropriate standard of review should be "intermediate scrutiny." (pp. 20-25) The court found that it "is not fairly debatable" that "same gender couples (the LGBT community) are a discrete group who have been subjected to a history of purposeful unequal treatment." (p. 22) With respect to whether sexual orientation is "immutable," the court stated that the question was not whether it was possible for a person to change this characteristic, but rather
whether the characteristic is so integral to the individual's identity that, even if he or she could change it, would it be inappropriate to require him or her to do so in order to avoid discrimination? (p. 25)
Third, in deciding the factual question as to whether same-sex couples are as good at parenting as opposite sex couples, the New Mexico Supreme Court rejected religion and embraced science. As to religion, the court stated:
Although this question arouses sincerely-felt religious beliefs both in favor of and against same-gender marriages, our analysis does not and cannot depend on religious doctrine without violating the Constitution. (p. 7)
Instead, in finding that same-sex couples are as capable as opposite-sex couples at raising children, the Court cited the amicus brief of the American Psychological Association, as well as a number of published sociological studies. (p. 28) The court noted that
In this case, no one denies that LGBT individuals are fully capable of entering into the kind of loving and committed relationships that serve as the foundation for families, or that they are capable of responsibly caring for and raising children. (p. 28)
Fourth, and most importantly, the New Mexico Supreme Court made it clear that it simply didn't matter what the standard of review was -- that the existing law excluding gay and lesbian couples from the institution of marriage is not rational -- that it doesn't even pass the "rational basis test." In the end, the Court struck down the law because of two simple ideas: the current law does nothing to help the children of heterosexual couples, yet does great harm to the children of same-sex couples. Here are the court's findings on those two points:
We fail to see how depriving committed same-gender couples, who want to marry and raise families, of federal and state marital benefits and protections will result in responsible child-rearing by heterosexual married couples. In the final analysis, child-rearing for same-gender couples is made more difficult by denying them the status of being married and depriving them of the rights, protections, and responsibilities that come with civil marriage. (p. 29)
Excluding same-gender couples from civil marriage prevents children of same-gender couples from enjoying the security that flows from the rights, protections, and responsibilities that accompany civil marriage. There is no substantial relationship between New Mexico's marriage laws and the purported governmental interest of responsible child-rearing. There is nothing rational about a law that penalizes children by depriving them of state and federal benefits because the government disapproves of their parents' sexual orientation. (p. 30)New Mexico is the 17th state to recognize marriage equality for same-sex couples.