The landmark decision by the Massachusetts Supreme Judicial Court Tuesday went further than any court yet toward legalizing gay marriage in the United States.

But couples eager to make their union official can't start lining up at the courthouse today. The tribunal stopped short of ordering the state to start issuing marriage licenses. Instead, it ruled the state's denial of gay marriage unconstitutional — and gave the Legislature 180 days to resolve the issue. This marks the first time a high court has ruled that civil marriage between a same-sex couple is a state constitutional right.

Republican Gov. Mitt Romney denounced the ruling but said there is little the state could do beyond pursuing a constitutional amendment.

"I agree with 3,000 years of recorded history. I disagree with the Supreme Judicial Court of Massachusetts," he said. "Marriage is an institution between a man and a woman . . . and our constitution and laws should reflect that."

The ruling means that the cultural divide over one of the most contentious issues in America will likely only deepen from here. Gay rights activists hope it will bolster their cause in other parts of the country, while conservative groups are equally determined to use it to solidify a growing backlash.

"This is the pre-eminent wedge issue," says independent pollster John Zogby. Now it has even greater "potential to be a wedge issue in 2004."

In its 4-to-3 ruling, the court held that "barring an individual from the protections, benefits and obligations of civil marriage solely because that person would marry a person of the same sex violates the Massachusetts Constitution."

Unlike court decisions in Hawaii and Vermont, the Massachusetts tribunal didn't send the decision back to a trial court or explicitly allow the Legislature to create its own solution. Instead, the court gave legislators and state regulators 180 days to adapt state law to the more expansive definition of marriage set out in its decision.

"It's a victory" for same-sex marriage advocates, says Kate Silbaugh, a family-law professor at Boston University. "This is the most expansive decision there has been."

The court redefines marriage as the voluntary union between two persons — a definition adopted earlier by a court in the Canadian province of Ontario. The ruling emphasizes the "enormous private and social advantages" that only marriage brings.

As a result, Silbaugh, says the Massachusetts high court is not likely to accept civil union as an acceptable alternative if offered by the Legislature.