WASHINGTON — Gay marriage supporters see 41 reasons to fret over the Supreme Court’s decision to take up the case of California’s ban on same-sex unions.

While nine states allow same-sex partners to marry, or will soon, 41 states do not. Of those, 30 have written gay marriage bans into their state constitutions.

That fact is worrisome to those who firmly believe there is a constitutional right to marry, regardless of sexual orientation, but who also know that the Supreme Court does not often get too far ahead of the country on hot-button social issues.

“Mindful of history, I can’t help but be concerned,” said Mary Bonauto, director of the Civil Rights Project at Gay and Lesbian Advocates and Defenders and a leader in the state-by-state push for marriage equality.

Bonauto was speaking before the court decided on Friday to take up cases on California’s constitutional ban on gay marriage and a federal law that denies to gay Americans who are legally married the favorable tax treatment and a range of health and pension benefits otherwise available to married couples.

In 2008, California voters approved the ban, Proposition 8, after the state Supreme Court ruled that gay Californians could marry. Since then, a federal appeals court struck down the constitutional provision, but did not authorize the resumption of same-sex marriages pending appeal.

Bonauto identified three earlier seminal rulings that once and for all outlawed state-backed discrimination, and observed that in each case the number of states that still had the discrimination on the books was far smaller.

Thirteen states still had laws against sodomy when the court said in 2003 that states have no right to intrude on the private, personal conduct of people, regardless of sexual orientation.

Interracial marriage still was illegal in 16 states in 1967 before the high court outlawed race-based state marriage bans.

In 1954, when the court issued its landmark decision in Brown v. Board of Education, 17 states had formally segregated school systems.

Cornell University law professor Michael Dorf said those cases illustrate a widespread misperception about the justices.

“There is a commonly held but inaccurate view that the Supreme Court does is to impose its views on the country. It very rarely does that. Much more frequently, it will take a view that is either a majority in some place or a majority of elite opinion, and speed up acceptance,” said Dorf, who was a Supreme Court law clerk to Justice Anthony Kennedy.

The forces that mounted the legal challenge to Proposition 8 have said all along that the right to marry is so fundamental that it should not depend on success at the ballot box or the votes of state legislatures. Washington lawyer Theodore Olson, representing gay Californians who wish to marry, said he will argue that there is a “fundamental constitutional right to marry for all citizens.”

But are there five justices, a majority of the court, willing to endorse that argument?

The fear among gay marriage proponents is that the court will refuse to declare that states can no longer define marriage as the union of a man and a woman, because to do so might provoke a backlash in public opinion and undermine acceptance of its authority.

A high court loss for gay marriage advocates would prevent same-sex marriages in the nation’s largest state. It would not affect the District of Columbia and the nine states — Connecticut, Iowa, Maine, Maryland, Massachusetts, New Hampshire, New York, Vermont and Washington — where gay couples can or soon will be able to marry.

But it could push back the day that many in the gay rights movement, looking at strong support for gay marriage among younger Americans, see as inevitable: the Supreme Court’s endorsement of full marriage equality nationwide.

Commenting after the court’s action, Bonauto said she believes the court can uphold an appeals court ruling that struck down Proposition 8 in a way that applies to California only and “leave to a later day questions about broader bans on committed same-sex couples marrying.“

Opponents of gay marriage look to another court case, Roe v. Wade, that they say should serve as a cautionary tale.  In 1973, the court voted 7-2 to declare that the Constitution protects a woman’s right to an abortion.

“Should the Supreme Court decide to overturn the marriage laws of 41 states, the ruling would become even more divisive than the court’s infamous Roe v. Wade decision,” said Tony Perkins, president of the Family Research Council. “Marriage, unlike abortion laws in the 1970s, has been incorporated into the state constitutions of 30 states. Voters in these states will not accept an activist court redefining our most fundamental social institution.”

To a degree, Perkins and Bonauto get some support from one of the nine people with a say in the matter, Justice Ruth Bader Ginsburg.

In February, Ginsburg questioned the timing of the abortion decision and suggested it may have contributed to the ongoing bitter debate about abortion.

“It’s not that the judgment was wrong, but it moved too far too fast,” Ginsburg said at Columbia University.

At the time of Roe v. Wade, abortion was legal on request in four states, allowed under limited circumstances in about 16 others, and outlawed under nearly all circumstances in the other states, including Texas, where the Roe case originated.

The court could have put off dealing with abortion while the state-by-state process evolved, she said. Or her predecessors could have struck down just the Texas law, which allowed abortions only to save a mother’s life, without declaring a right to privacy that legalized the procedure nationwide, Ginsburg said.

“The court made a decision that made every abortion law in the country invalid, even the most liberal,” Ginsburg said. “We’ll never know whether I’m right or wrong ... things might have turned out differently if the court had been more restrained.”

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