To the extent that marriage represents a property contract between two people, and not merely an expression of their love, states are requiring couples to sign on the dotted line. The centuries-old institution of common-law marriage is dying away.

Only 10 states still recognize new common-law marriages, which occur when a man and a woman cohabitate and declare themselves to be husband and wife. "Many sound reasons exist to abandon a system that allows the determination of important rights to rest on evidence fraught with inconsistencies, ambiguities and vagaries," wrote Pennsylvania Commonwealth Court Justice Bonnie Brigance Ledbetter in a September decision that ended the practice in that state.

Common-law marriages date from colonial times, when the country was mostly rural, transportation was difficult and there weren't enough ministers or justices of the peace to go around. In our current era, it's easy enough for couples to obtain a marriage license and find someone vested with the authority to perform the nuptials. (The complexities of choosing caterers and photographers for a formal wedding celebration are another matter entirely.)

Because there is no legal documentation, it's always been very difficult to prove--or disprove--whether a couple had entered into a common-law marriage. Disputes are especially common after one of the alleged spouses has died. A supposed wife or husband shows up to claim a share of the inheritance or insurance and it becomes a question of his or her word against a dead person's as to whether they were, in fact, married.

"It was only a matter of time before it was invalidated or terminated," says Stewart Greenleaf, chairman of the Pennsylvania Senate Judiciary Committee, who notes that legislators would have acted if the courts hadn't beat them to it. He says that it's become too confusing for health insurance carriers to determine whether they are obligated to offer coverage to cohabitants claiming to be married. "It's important for them to go through the formal ceremony so there's no doubt about it."

It's rare that disputes about common-law marriages arise over anything except money. That's one reason why insurance companies, although not making the issue a major priority, have typically supported attempts to curb the practice. "The standards of proof were so loose that someone could easily maintain a claim," says John Mayoue, a family lawyer in Georgia, which stopped recognizing such marriages in 1997. "A lot of states were finding these claims or common-law marriages were frankly fraud."

The standards of what constitutes a common-law marriage vary by state. It used to be that couples were required to live together for a fixed period of up to seven years before they were considered married. None of the states that still recognize common-law marriages requires a specific time commitment. But couples do have to present themselves as married--sharing not just a home but also the same surname, joint income tax returns and the intention of getting married.

Some lawyers maintain that such marriages remain useful in protecting the rights of individuals who otherwise might be denied their rights to shared property. "From a purely legal point of view, it does solve some problems from time to time," says Oklahoma state Representative Frank Davis. Where undocumented marriages do cause confusion, Davis says, the courts are there to clear things up.

Mayoue argues that because most states have changed their laws in recent years to allow people who live together outside of the constraints of marriage to enter into enforceable contracts with each other, there's no longer the same need for common-law protections. In other words, people don't need to get married to buy a house or enter into child-custody disputes together.

"This is something that has way outlived its necessity," says Oklahoma state Representative Ray Vaughn, who has been trying to ban the practice in the Sooner State for several years. "If they want to obtain benefits as the result of their relationship, it seems to me that there should be some kind of written evidence of the existence of that relationship. It could be a statement. You could do it on the back of an envelope or a napkin."