Boston ? Talk about shotgun marriages. The Massachusetts Legislature finally found a way to unite the opponents on either side of the gay marriage debate. These enemies are now wed in anger at the politicians.

On Monday, the Legislature narrowly approved an amendment to the state constitution that would simultaneously ban same-sex marriages and establish civil unions. This dual deal was taken as a piece of double-dealing. It dismayed the folks bearing posters that read “No Civil Rights for Sodomites” almost as much as those carrying placards that said “No Discrimination in the Constitution.”

One gay activist called the law a “kinder, gentler way to take away our rights” while an opponent called it “blackmail.” For a moment I thought we’d see both groups lock arms and march up Beacon Hill singing “We Shall Overcome.”

They may yet overcome the amendment. In order to change the state constitution, the bill, which only passed 105-92, has to pass the Legislature again next year and then win at the ballot box in 2006. The marriage of convenience between enemies may last just long enough to prevent passage.

What a wedding season this has been. In 2000, when the Vermont Legislature under court order invented “civil unions,” the idea was considered so radical that the citizens thought the Ben & Jerry’s ice cream would curdle.

Then last November the Massachusetts high court struck down the ban on same-sex marriage. When the court was asked if civil unions would do — or “I do” — instead, the justices ruled no. They said, “Separate is seldom, if ever, equal.”

Since then, we’ve seen the marriage office open and close in San Francisco. We’ve had wedding vows and/or rows from New Paltz, N.Y., to Portland, Ore. And we’ve had a field day for comics who want to know if the only men in America who aren’t commitment-phobic are gay.

In Washington, the president came out for an amendment to the U.S. Constitution. The House Judiciary Committee opened hearings on Tuesday, but the proposal seems to have slipped as far down the list of Bush priorities as the proposed trip to Mars.

Meanwhile, the image of gay Americans has become strictly Venus. It’s the breathtakingly conservative photo op of two mommies or daddies, a couple of kids and a copy of “Attachment Parenting.”

Back in Massachusetts, however, things are a bit more complicated. We are still are under a court ruling to begin the first state-sanctioned gay marriages on May 17. But we now also have a constitutional amendment that, if passed, could prohibit same-sex marriages in 2006. As some couples celebrate their second anniversary, the wedding bells could go silent for others.

This has led the Republican governor, Mitt Romney, who must wish he were still running the Olympics, to vow to ask the court to stay its ruling until the 2006 vote. This, says Romney, an opponent of same-sex marriage, would avoid confusion.

Confusion? It’s unlikely that the court would hold up its own ruling on the possibility that it could be overturned. But imagine that precedent.

And if we are really worrying about legal confusion, has anyone noticed the kind of mess produced by a two-tier marital structure? We already have something approaching chaos in custody disputes between gay partners.

In Massachusetts, we even have one case in which a couple broke up before the artificially inseminated child was born. Does the other parent have to pay child support? We have a mind-boggling case in which the egg-donor mother and the gestational mother of 5-year-old twins split. Who gets custody?

Indeed, while everyone is in the first blush of wedding plans, the laws that would extend the rights and privileges of marriage would also — ta da — extend the laws governing divorce to gay couples. Lucky them.

It’s stunning to see how quickly civil union has become the moderate position, and the pace of this change isn’t slowing down. Every poll shows that young Americans are more accepting of gay marriage than their elders. We’re in the middle of a shift toward acceptance of full rights for gay couples. This is no time to amend constitutions — federal or state — to limit either citizen’s rights or social change.

So the Massachusetts Legislature had a chance to reach across a cultural divide. Instead, it collapsed, exhausted, into a muddle. If this state gets two and a half years of experience before an amendment comes up for a popular vote, we may yet prove that same-sex marriage is not the end of Western civilization.

For the moment, however, the only union the legislators have created is between enemies who each regard the amendment as unprincipled. And this union, I assure you, isn’t civil.

Ellen Goodman is a columnist for Washington Post Writers Group.