My first reaction to the Supreme Court decision overturning the Defense of Marriage Act and leaving California’s Proposition 8 overturned was to think: “Note to future historians: we just revoked the Edict of Milan.” History buffs will recall that this edict was Constantine’s fiat offering toleration to Christians, issued almost exactly 1,700 years ago. That golden moment marked the end of the persecuted Church and the beginning of Christian civilization.

There were dark moments, too, which started when Constantine’s successor Theodosius began to persecute Roman pagans and use the state’s coercive power to aid the Church. Like most modern Christians, I deplore that decision and all that flowed from it—the heresy trials, inquisitions, pogroms, and persecutions that dragged on for centuries. But I’m not surprised: while some kind of state is necessary, it is also very dangerous—doubly so, given our fallen nature. Power doesn’t just corrupt, it attracts the already corrupt, the envious, the resentful who crave the chance to micromanage and punish. How tempting it is for entrenched and lazy businessmen to use the police and prisons to enshrine their wealth in law; for sullen, slacking workers to quash fair competition; for corrupt and worldly churchmen to silence dissenters and reformers. (Imagine if the bishops who shuffled pedophiles around had held the power to censor the press.) It is rare indeed for a state to resist all the pressures of those who would distort the rule of law and ignore the common good to serve their private interests; for citizens with strong opinions on how their neighbors should live to respect their human dignity and leave them largely alone; for institutions of civil society to spurn the proffered privileges (and secret strings) that the state extends.

The rise of same-sex marriage marks the end of the long, slow fight the Christian church has waged to keep legal marriage analogous to a sacramental covenant. But these Supreme Court decisions and all their consequences arguably became inevitable some 200 years ago, when the French revolutionaries created “civil marriage,” removing the church’s legal jurisdiction over this contract. At that moment, the meaning of marriage lost its anchor in an authoritative reading of man’s nature and flew off like a kite into the winds of human passions and opinion. We have been rushing about ever since attempting to grab the string and tie it to something else—the best interests of children, the common good, “republican virtue” (in France)—but nothing resists the gale.

Sexual decisions are so intimate and so important to people that it takes a really potent force to goad them into self-restraint; either deep religious conviction or crushing social pressure is typically required. In their absence, people will do what they feel they must, and those of us who try to draw fine moral distinctions will seem like busybodies and prudes. In elite opinion now—which is common opinion tomorrow—–those who hold to traditional Christian marriage are morally no better than racists.

That’s where we are. Now what do we do? Should we wage a legal Verdun in each of the 50 states to revive the pale, exhausted ghost of “marriage” that Bill Clinton’s DOMA defended? Thanks to no-fault divorce, it was already the least enforceable legal contract on earth—–more fragile by far than credit-card debt, not to mention back taxes and student loans. It was, in essence, a weak legal partnership and a temporary sex pact that for some reason excluded homosexuals. Is this a hill worth dying on?

On the other hand, we should be very worried about the implications of marriage’s redefinition for the liberty of Christian citizens and their institutions. How far are we, really, from a court ordering the Catholic churches of California to perform homosexual unions—–and when the bishops refuse, fining the church into bankruptcy? Are we really that confident that future Supreme Court justices will see the First Amendment as trumping their inflated reading of the Fourteenth? Obviously, we have to fight. The issue is over what ground and with what weapons.

The ghost of civil marriage does not deserve our loyalty. In fighting for it, we are going against the grain of American individualism and goading libertarians to join our enemies—–who will, as always, use them then toss them aside. Instead, we can make common cause with libertarians and invoke for our self-defense some cherished American principles, such as freedom of association, contract, and even religion.

And here is how: instead of demanding that the state enforce a single model of marriage contract—–one that is already hopelessly compromised—–we embrace freedom of contract and insist on it for ourselves. Why is it, we should ask, that Christians cannot draw up a legal contract that binds them as their sacrament says it does: for life? Why can’t we embrace that difficult promise and freely agree to have the state enforce it? Last time I was on a casino boat in Baton Rouge, you could mortgage your house on an ATM—and the state would enforce it. Why is it that Christian marriage remains an unenforceable, meaningless contract? As things stand now, in many states gay marriage is legal while Christian marriage is not.

Let’s abandon the notion of a single, normative marriage contract which is all that the state will enforce. Let private individuals (or their churches) produce contracts that lawyers can vet, which once signed will be enforced by the state. These contracts can be polygamous, homosexual, or celibate for all I care. Christian marriage can be one of those contracts. Churches that are serious about marriage can make signing a really solid (“covenant”) contract a condition of marrying in their place of worship. Every parish can have the boilerplate on its website: sign here or go find another Gothic building for your ceremony. To protect the liberties of everyone involved in this newly pluralist society, certain anti-discrimination laws also must be changed. If a gay employer doesn’t wish to hire Catholics, he should have that right—and the same for the goose as the gander.

An arrangement like this should entirely satisfy the libertarian demand for freedom of association and contract—and claim it also for Christians. Christians should be satisfied that our model will prevail without the assistance and entanglement of the state. Of course, the Rousseauian left will not be satisfied: they will settle for nothing less than state-enforced “virtue” and mandatory “freedom.” But with this strategic retreat to more defensible ground, Christians and other social traditionalists will gain breathing room. We don’t need a Theodosius, but without a Constantine we may well find ourselves in the catacombs once again.

John Zmirak is author, most recently, of The Bad Catholic’s Guide to the Catechism.