Earlier this year, Shannon Robinson stood on the floor of the New Mexico Senate and confessed to his colleagues that he had broken the law. In fact, he was a repeat offender. He wasn't guilty of tax evasion or theft, though. Instead, he had broken the state's statute against cohabitation, which dated from 1859. "I'm a criminal," he told them. "I have violated that law for a good chunk of my life."

Robinson's tongue-in-cheek remarks came in the midst of a debate that ended with the Senate voting to repeal New Mexico's strictures against adults living together in sin. Neighboring Arizona also repealed its anti-cohabitation law this year, but similar laws preventing "lewd and lascivious" living arrangements between men and women are still on the books in seven states: Florida, Michigan, Mississippi, North Carolina, North Dakota, Virginia and West Virginia.

Statistics, however, clearly indicate that momentum in society is going the other way. The number of unmarried-couple households has nearly doubled over the past decade in those seven states, compared with a 15 percent rise elsewhere. Other states and cities are more likely to debate granting benefits to domestic partners than to outlaw such arrangements in the first place. Common-law marriages are recognized in 10 states, with four other states recognizing common-law marriages formed before particular dates. In addition, New Hampshire put a twist on the old vow "till death do us part" by recognizing common-law marriages only at death for purposes of probate.

"They're like a vestigial organ," Robinson says of anti-cohabitation laws. "The Senate knew it was something that was way past its relevance in today's world."

Couples living together where it's still against the law have little reason to fear prison sentences or fines since the criminal penalties are rarely enforced. One of the few places where the law is vigorously upheld is in the courtroom of Carl Horn III, a federal magistrate in Charlotte, North Carolina. As a condition of release on bail, regardless of the charge, Horn insists defendants marry their live-in loves or find another place to live. "I am not seeking to `enforce morality,'" Horn says. "Rather, my more modest purpose is to enforce responsibility."

The fact that cohabitation laws are generally enforced erratically and thus unfairly, however, has been used as an argument that they should be abolished. These laws also have ancillary consequences aside from their criminalizing and stigmatizing effects. The U.S. Internal Revenue Service does not allow filers to take advantage of deductions if they are in violation of local law. A person who might claim a live-in lover as a dependent in most states cannot do so in the seven states banning cohabitation. Despite being scored at a cost of $500,000, Arizona's repeal was nevertheless sponsored by the House Ways and Means Committee chairman, Steve May.

The Arizona repeal effort was blocked for seven years by legislative leaders who finally lost power due to term limits and a partisan tie in the state Senate. "Fortunately, we had the votes," May says. Now that the state's ban on cohabitation has been lifted--along with bans on sodomy and adultery--even social conservatives acknowledge that the battle there is over.

"The increase in cohabitation and decrease in marriage is a destructive factor in our society, and the state ought not to encourage it," says Len Munsil, president of the Center for Arizona Policy, which lobbied against repeal. Nevertheless, Munsil counseled some legislators who wanted to place on the ballot an initiative restoring the ban that they should skip it, saying it would be a losing effort. "I've told people for years, once the laws were repealed, they're gone for good," Munsil says.