HARTFORD, Conn. - An attorney for eight gay couples told the state Supreme Court yesterday that their constitutional rights had been violated by the state's refusal to grant them marriage licenses.

Connecticut was the first state to allow civil unions without court pressure, but the couples say that is not enough.

They want the court to rule that the state's marriage law is unconstitutional because it applies only to heterosexual couples, effectively denying gay couples the financial, social and emotional benefits of marriage.

"What is denied to these families is something that goes to the heart of equal protection, which is the right to be part of the fabric of society when they are just the same as other couples and other families," said their attorney, Bennett Klein.

Assistant Attorney General Jane Rosenberg, representing the state, argued that civil unions gave gay couples the same rights by state law as married couples.

"Is the legislature constitutionally required to use the word marriage when it's referring to the package of rights and benefits it has given to same-sex couples?" Rosenberg asked. "The answer is clearly no."

Arguments wrapped up after about three hours yesterday, and the justices are expected to rule later this year.

Attorneys on both sides say a decision in the couples' favor could have nationwide implications for states that have adopted or are considering civil-union-like legislation.

Currently, only Massachusetts allows same-sex couples to marry. New Jersey, Connecticut, Vermont, California, Maine and Washington have laws allowing either civil unions or domestic partnerships, with New Hampshire set to join in January. Hawaii extends certain spousal rights to same-sex couples and cohabiting heterosexual pairs.

The Connecticut couples who sued have been together from 10 to 32 years and say civil unions are inferior to marriage and violate their rights to equal protection and due process.

Married couples have federal rights related to taxes, Social Security beneficiary rules, veterans' benefits and other laws that people in civil unions do not have. Because civil unions are not recognized nationwide, other rights, such as the ability to make medical decisions for an incapacitated partner, disappear when couples cross state lines.