A story published today in the International Herald Tribune reports that a little-known religious procedure authorizing temporary marriages is by some unmarried couples as a way to have sex without getting in trouble with the law.

An example is Maryam, a hairdresser, and Karim, a home appliance salesman, who for five years carried on a love affair, meeting secretly at the house where Karim lived with his parents. The young couple's relationship was officially sanctioned by Iran's Islamic Republic, even though unmarried couples who have sex or even date and hold hands can be arrested, fined, even flogged. That is because Maryam and Karim were married.

Kind of.

They had a valid contract of temporary marriage.

The story explains that Iran is a country where rules are fluid, where people of all classes and degrees of religiosity pride themselves on finding loopholes in the Islamic system. Temporary marriage, or sigheh, is one of the oddest and biggest.

The practice of temporary marriage is said to have existed during the lifetime of the Prophet Mohammed, who is believed to have recommended it to his companions and soldiers. The majority Sunni sect in Islam banned
it; the minority Shiite sect did not.

Historically, the practice was used most frequently in Shiite-dominated Iran by pilgrims in Shiite shrine cities like Meshed and Qum. Pilgrims who traveled had sexual needs, the argument went. Temporary marriage was a legal way to satisfy them.

Maryam and Karim chose temporary marriage for a practical reason.

''We went out a lot together, and I didn't want to get into trouble,'' said Maryam, 31. ''We wanted to have documents so that if we were stopped on the street we could prove we weren't doing anything illegal.''

Their ''marriage'' ritual was simple. Even though they could have sealed the contract privately, they went to a cleric in a marriage registry office in Tehran with their photographs and identity papers.

Maryam had been forced into a hollow marriage at 15 to an opium-smoking, womanizing factory owner nearly two decades her senior who divorced her nine years later; so she brought along her divorce decree. If she had been a virgin, she would have needed her father's permission to marry.

The couple could have become married for as short a time as a few minutes or as long as 99 years. They could have specified whether and how much money Maryam would be paid as a kind of dowry, or how much time they would spend together. Instead, they decided on a straightforward contract of six months, which they renewed again and again.

What was unusual about Maryam's situation was her willingness to talk about it. Despite its religious imprimatur, temporary marriage has never been popular in Iran. Tradition dictates that women be virgins when they marry; even when they are not, they should pretend to be. Many Iranians regard sigheh as little more than legalized prostitution, especially since it is an advertisement that a woman is not a virgin.

But now an unusual mix of feminists, clerics and officials have begun to discuss sigheh as a possible solution to the problems of Iranian youth. An extraordinarily large number of young people (about 65 percent of the population is under 25) combined with high unemployment mean that more couples are putting off marriage because they cannot afford it. Sigheh legally wraps premarital sex in an Islamic cloak.

''First, relations between young men and women will become a little bit freer,'' said Shahla Sherkat, editor of Zanan, a feminist monthly. ''Second, they can satisfy their sexual needs. Third, sex will become depoliticized. Fourth, they will use up some of the energy they are putting into street demonstrations. Finally, our society's obsession with virginity will disappear.''

Even conservatives like Mohammed Javad Larijani, a U.S.-educated former legislator, favor temporary marriage. As he put it: ''What's wrong with temporary marriage? You've got a variation of it in California. It's called a partnership. Better to have it legal than have it done clandestinely in the streets.''

Advocates of temporary marriage also point out that children of such unions are legitimate and entitled to a share of the father's inheritance. But the popular response has not been favorable. After ''The Hope of Youth,'' a weekly, ran an article in favor of sigheh, readers called and wrote in with attacks.