The debate over same-sex marriage has roiled for over a decade. On one side are people who believe that marriage is properly limited to one man and one woman. On the other are those who argue that lack of access to marriage is unfair to gay couples, because it deprives them of benefits that flow from the marriage certificate, such as survivor rights, hospital visitation and insurance coverage.

In recent years, a sort of middle ground has developed. Called civil unions or domestic partnerships, this new arrangement is often promoted as a way to preserve traditional marriage while bestowing many of its government benefits on gays.

The major Democratic presidential candidates have embraced civil unions as a compromise on same-sex marriage. Some Minnesotans promote the approach as well.

But last week, this middle ground disappeared -- courtesy of the California Supreme Court. In ruling California's marriage laws unconstitutional, the court made clear that, far from preserving traditional marriage, domestic partnerships are actually likely to hasten its demise.

The California court has no direct impact on Minnesota, but it is often viewed as a bellwether for rulings around the country.

California citizens have tried hard to find a middle ground on same-sex marriage. In 2000, they approved a state initiative defining marriage as a one-man/one-woman institution with 61.4 percent of the popular vote. But voters also wanted to extend government benefits to gay couples. In 1999, the California Legislature had done just that by adopting the Domestic Partner Act.

Over the years, the Legislature added to the benefits that registered domestic partners enjoy. These range from automatic inheritance to equal treatment on state income taxes. Today, as the court noted in its recent decision, California gives same-sex couples the opportunity "to obtain virtually all of the legal benefits, privileges, responsibilities, and duties that California law affords to and imposes upon married couples."

Despite this, the Court ruled last week, in a 4-3 vote, that the state's one-man/one-woman marriage law violates the California constitution.

The court put no stock in the state's argument that same-sex and opposite-sex couples already have equivalent rights under California law. In fact, the majority found that the Legislature's decision to treat gay relationships as worthy of marriage-like benefits actually bolstered plaintiffs' argument that domestic partnerships are discriminatory. Since the Legislature has treated same-sex and opposite-sex couples equally, said the court, withholding the marriage label from gays is a "mark of second-class citizenship."

Ironically, the court suggested that it might have reached a more moderate conclusion -- such as requiring the Legislature to institute domestic partnerships, rather than to redefine marriage -- if lawmakers had not already given substantial benefits to gay couples.

Minnesotans can draw two lessons from the California decision. First, it vindicates the approach taken by the proposed Minnesota marriage amendment, which the Minnesota House of Representatives passed in 2006 but the DFL-controlled Senate killed by keeping it bottled up in committee. The amendment would have prohibited both same-sex marriage and civil unions. Opponents sometimes slammed this dual prohibition as mean-spirited, but the California decision now reveals it to be far-sighted.

Second, the California decision vindicates Minnesotans who argue that a constitutional amendment is the only way to safeguard traditional marriage. During the 2006 debate, then-Senate Majority Leader Dean Johnson and OutFront Minnesota both maintained that the amendment was unnecessary, because our state already has a "defense of marriage" act and because the Minnesota Supreme Court rejected same-sex marriage in a 1971 case.

But when it tossed out California's one-man/one-woman voter initiative -- which the state's Legislature cannot overturn on its own -- the California majority showed how far arrogant, activist courts will go in disregarding the will of the people.

Fallout from the California decision may create two perverse reactions that will haunt same-sex marriage supporters.

First, citizens who once favored more benefits for gay couples may begin to oppose them, knowing now that expanded benefits and same-sex marriage constitutionally go hand in hand.

Second, support may grow for amendments that enshrine traditional marriage in state constitutions. In California, citizens will likely have a chance to vote on such an amendment in November. Before their state's high court tossed out California marriage laws, voters there might have paid the subject little heed, confident that they had found middle ground.

Anyone who has followed the abortion debate knows what happens when a court cuts out the middle ground, as the U.S. Supreme Court did on abortion 35 years ago in Roe vs. Wade. Toxic social division is inevitable when courts usurp the people's rights.

Katherine Kersten • Join the conversation at my blog, Think Again, which can be found at