SWISS GRANT WOMEN EQUAL MARRIAGE RIGHTS

Swiss voters today narrowly approved a Government-sponsored law that gives women equal rights in marriage, eliminating the last national legal bastion of male supremacy.

Approval of the law, by 54.7 percent of about one million voters, marked a milestone in the nation's movement toward sexual equality under the law, which began in 1971 with approval of women's suffrage at the federal level, and continued in 1981 with the adoption of an equal rights amendment to the Constitution.

''We have made another step forward,'' said Elisabeth Kopp, who last year became the first woman to occupy a post in the seven-member Federal Council, the Swiss executive body elected by the Parliament. ''The first was with the woman's vote, and the second with the equal rights amendment in 1981,'' she said. ''Now we can rightly say here there have been no losers.''

Behind Others in Europe

Although Switzerland has often exhibited an innovative approach in other areas of social policy, such as its treatment of prisoners and drug users, it has lagged behind much of the rest of Western Europe in granting equal rights to women. Switzerland was the last Western democracy to grant women the right to vote and until today its laws had legally guaranteed a husband's supremacy in the marriage.

The old laws, described by the Government as ''incompatible with female dignity,'' guaranteed the husband's role as head of the family by allowing him to prevent his wife from working, choose the couple's place of residence, and manage the savings his wife had before the marriage as well as her inheritance. It also prevented a wife from opening a bank account without her husband's approval.

The new law, passed by the upper and lower houses of the Swiss Parliament last year with minor opposition from conservative members, was submitted to the electorate in a referendum after opponents conducted a petition drive. It pledges spouses to ''harmonious cooperation;'' deletes all references designating a head of the family or male decision-maker and financial manager, and obliges each spouse to provide the other with information on income, property and debts.

Under Switzerland's system of direct democracy, opponents or proponents of a measure can bring it to a popular vote if they succeed in gathering at least 50,000 signatures.

Some Term It 'Anti-Marriage'

Despite the lack of serious opposition in the Parliament, opponents belonging to conservative and traditional organizations and including both men and women maintained that the move was ''anti-family'' and ''anti-marriage,'' and said it would turn marriage into a business-like partnership.

Conservative religious opponents, including at least one Protestant pastor, had also cited biblical passages in support of the man's leading role in a marriage.

Although the measure won narrow approval from the electorate nationwide, voters in 12 of Switzerland's 26 cantons, or states, rejected it. Among the states voting no was Appenzell, a predominantly rural and staunchly traditional area where women are still forbidden the right to vote on local issues. Other rural and mountainous cantons, primarily in the northern and eastern German-speaking regions, voted against the law, while more liberal and populous areas such as Zurich and Basel voted for it, as did the French- and Italian-speaking regions. In Bern, the capital, the vote was a virtual draw, with a margin of 97 voters out of more than 250,000 tipping the balance against the measure.

Although the law now legally guarantees women's rights in marriage, individual families have long made their own adjustments depending on their adherence to traditional values or their desire to adopt social positions more in tune with neighboring countries such as France and West Germany. Only Liechtenstein, a tiny German-speaking monarchy between Switzerland and Austria, has proceeded more slowly. It granted women the right to vote last year.