Religious and conservative groups called the ruling an outrage but not unexpected, and spoke of steps to enact a constitutional ban on gay marriage. Peter Wolfgang, executive director of the Family Institute of Connecticut, blamed “robed masters” and “philosopher kings” on the court. “This is about our right to govern ourselves,” he said. “It is bigger than gay marriage.”

But the state, a principal defendant in the lawsuit, appeared to be resigned to the outcome.

Gov. M. Jodi Rell said that she disagreed with the decision, but would uphold it. “The Supreme Court has spoken,” she said. “I do not believe their voice reflects the majority of the people of Connecticut. However, I am also firmly convinced that attempts to reverse this decision, either legislatively or by amending the state Constitution, will not meet with success.”

Attorney General Richard Blumenthal said his office was reviewing the decision to determine whether laws and procedures will have to be revised — local officials will issue marriage licenses to gay couples without question, for example — but he offered no challenge and said it would soon be implemented.

The case was watched far beyond Hartford. Vermont, New Hampshire and New Jersey all have civil union statutes, while Maine, Washington, Oregon and Hawaii have domestic partnership laws that allow same-sex couples many of the same rights granted to those in civil unions. Advocates for same-sex couples have long argued that civil unions and domestic partnerships denied them the financial, social and emotional benefits accorded in a marriage.

The legal underpinnings for gay marriages, civil unions and statutory partnerships have all come in legislative actions and decisions in lawsuits. Next month, however, voters in California will decide whether the state Constitution should permit same-sex marriage.

The Connecticut case began in 2004 after the eight same-sex couples were denied marriage licenses by the town of Madison. Reflecting the contentiousness and wide interest in the case, a long list of state, national and international organizations on both sides filed friend-of-the-court briefs. The plaintiffs contended that the denial of marriage licenses deprived them of due process and equal protection under the law.