The historic constitutional test of gay marriage rights unfolds Tuesday as the U.S. Supreme Court takes up California’s same-sex marriage ban, a case in which opponents to the ban seek not a narrow victory, but full participation by gay couples in the fundamental right to marry.

More than 40 years have passed since the high court faced its first and only same-sex marriage challenge, one brought by Minnesotan Richard James "Jack" Baker. The justices, without comment, dismissed Baker v. Nelson for want of a substantial federal question. There is little doubt that the Roberts Court will have much more to say, and what it says could well define the court for years to come.

The California case, Hollingsworth v. Perry, is the first of two arguments. A challenge to the federal Defense of Marriage Act, Windsor v. U.S., follows on March 27. That the stakes are high can be seen in the outpouring of amicus briefs, nearly 100 in Perry and close to 80 in Windsor, spanning the political, legal, religious, social, business and labor spectrums.

Proponents of California’s Proposition 8 lost in the lower federal courts and now ask the justices whether the 14th Amendment’s equal protection clause permits California to define marriage as the union of a man and woman. But the ban’s opponents urge the high court to go beyond a California-specific ruling and to take the major step that, they contend, the Constitution envisions.

The case is rich with difficult legal questions, from the standing of the ban’s proponents to defend it to the constitutional standard of review, and it offers multiple off-ramps, or ways, for the justices to resolve the case.

"Regardless of what the Supreme Court decides, it is not going to settle the public debate we have on marriage any more than it settled the debate on abortion," said Austin Nimocks, senior counsel to the Alliance Defending Freedom, co-counsel to the Prop. 8 proponents in Perry. "And that is why we feel very strongly the Supreme Court should not impose a 50-state solution upon the country and should allow the citizens to continue to debate this and work on it through our democratic institutions."

Regardless of the court’s ultimate rationale, "the arguments in support of [gay marriage] restrictions have been thoroughly dismantled," said Prop. 8 opponents’ co-counsel David Boies of Boies, Schiller & Flexner, noting their success in the trial and appellate courts. "We believe a 50-state result is the right result under the due process clause and the equal protection clause."

The issues

As he has done in each court since the initial lawsuit against Prop. 8 was filed four years ago, Charles Cooper of Cooper & Kirk will defend the state marriage ban as well as the standing of his clients before the justices on March 26.

His clients include the official proponents of Prop. 8 — ProtectMarriage.com, a ballot measure committee led by Dennis Hollingsworth. They intervened to defend the ban after California officials refused to do so. Besides Nimocks, Cooper also has as co-counsel Andrew Pugno, counsel to ProtectMarriage.com.

Cooper will face Theodore Olson of Gibson, Dunn & Crutcher who along with Boies was hired by the American Foundation for Equal Rights to bring the lawsuit challenging Prop. 8. They represent two couples, Kristin Perry and Sandra Stier, and Paul Katami and Jeffrey Zarrillo. The city and county of San Francisco also intervened at trial as plaintiffs and they are represented by City Attorney Dennis Herrera. Olson will make arguments on their behalf.

The United States has entered the case on behalf of Prop. 8 opponents. Solicitor General Donald Verrilli Jr. will share argument time with Olson.

On the merits, Cooper argues that authorities in every academic institution that has studied marriage, as well as lawmakers and courts that have given legal recognition to marriage, have uniformly recognized throughout history that marriage is between a man and a woman. Its central purpose, he contends in his brief, "is to channel potentially procreative sexual relationships into enduring, stable unions for the sake of responsibly producing and raising the next generation."

Because same-sex relationships do not have the capacity to produce children, he adds, "they do not implicate this interest in responsible procreation and childrearing in the same way. The Equal Protection Clause does not require the State to ignore this difference." He accuses his opponents of creating a genderless, litigation-inspired conception of marriage that is contrary to the court’s and the historical understanding of that institution.

Olson counters that Prop. 8 supporters "seem to have no understanding of the privacy, liberty, and associational values that underlie this Court’s recognition of marriage as a fundamental, personal right." Their "state-centric construct of marriage means that the State could constitutionally deny any infertile couple the right to marry, and could prohibit marriage altogether if it chose to pursue a society less committed to ‘responsible’ procreation," he writes.

Prop. 8 violates due process, Olson argues, because it denies gay couples their fundamental right to marry without furthering a legitimate or compelling state interest. And it violates equal protection because by denying the right to marry on the basis of sexual orientation or the sex of one’s partner, it makes gay men and lesbians "unequal to everyone else," he adds, quoting the justices’ ruling in Romer v. Evans.

The two sides also spar over what standard of review the court should apply to Prop 8. Cooper argues that sexual orientation is unlike other suspect classifications, such as race and gender, and heightened scrutiny should not apply, only rational-basis scrutiny. Two of the traditional indicia of a suspect class — political powerlessness and immutability — are "plainly lacking in this case." Sexual orientation is not a trait determined solely by accident of birth, he argues, and gays and lesbians have substantial political power as indicated by their political victories.

Prop. 8 cannot pass any constitutional standard of review, according to Olson. He and the United States argue for heightened scrutiny, citing the long history of discrimination against gay men and lesbians because of their sexual orientation, the immutability of sexual orientation and their relative powerlessness to overcome a "deeply engrained" pattern of discrimination.

On the standing issue, Cooper relies on the California Supreme Court’s response to the U.S. Court of Appeals for the Ninth Circuit when asked if the Prop. 8 ballot sponsors had standing under state law. The state court said yes, giving them state-law authority. Olson counters the proponents have never contended they would suffer personal injury if gay marriages were allowed, and a mere desire to defend Prop. 8 is not sufficient for Article III standing.

The amicus briefs

The nearly 100 amicus briefs in the Perry case flesh out the key legal issues and offer the justices additional information about the religious, social, psychological and other ramifications of a ruling for or against Prop. 8.

"From our perspective, the goal is to have the amici express points helpful to the court and, given the page limitations, to add to the understanding of issues we may not have had the opportunity to brief in as much depth as we would like," said Gibson Dunn’s Christopher Dusseault, who coordinated the amicus effort for the Prop. 8 opponents. A key brief was filed on behalf of 100 or more notable social and political conservatives. "It highlights something critical to us from the beginning — marriage equality is not a liberal or conservative issue. It’s a matter of fundamental rights. For them to say this because they’re conservative, not in spite of being conservative — I think that’s really important," Dusseault said.

He also noted a brief by 200 corporations explaining how discrimination harms them and their employees, and a brief by gay parents countering the argument that children of gay parents do not fare as well as those of heterosexual parents. "The reality is science doesn’t support that argument at all," he said.

There are two different briefs, one filed by a broad coalition of civil rights groups and the other by law professors, addressing the factors for the heightened-scrutiny standard of review and why sexual orientation satisfies them.

On the pro-Prop. 8 side, a brief by 37 academics urges the justices to refrain from recognizing same-sex marriage because of the role of states as sovereigns and laboratories of democracy.

A group of historians in another brief argues there is no basis in the nation’s history, traditions or practices for recognition of same-sex marriages.

The Becket Fund for Religious Liberty warns the court that recognizing a gay marriage right could place religious organizations opposed to that right in jeopardy of substantial civil liability and penalties if they continue their religious practices.

Less than a week before the Supreme Court arguments, lawyers on each side were engaged in intense preparations.

Olson sat in a small windowless room in Gibson Dunn’s D.C. offices reviewing the trial record and the briefs and emailing questions to his legal team as they occurred to him, said Theodore Boutrous, a member of that team.

"This is probably the first case in the 26 years I’ve been working with Ted where we brought the case, knew it might go to the Supreme Court, and handled every single aspect of it with that possibility," Boutrous said. "It was a plan and a strategy and now we’re at the crucial moment we had envisioned. It affects so many people. We’ve tried to do everything possible to win."

On the pro-Prop. 8 side, "The preparations have been significant and ongoing," Nimocks said. "But we will be ready to defend the citizens of California and Prop. 8 on Tuesday."

Olson is "ready to go," Boutrous said. "Never before in history has a major civil rights issue landed at the door of the Supreme Court with this wave of public support. America is ready."

Whether the Supreme Court is, time will tell.

Marcia Coyle and Tony Mauro write for The National Law Journal, a Daily Report affiliate.