HONOLULU — A special session of the state Legislature that starts Monday could make Hawaii the next state to formally legalize same-sex marriage.
Many credit a Hawaii case that began in 1990 with prompting action on the issue of gay marriage in courts and state houses nationwide. That led Congress in 1996 to pass the federal Defense of Marriage Act, which was struck down this year by the Supreme Court.
The state allows civil unions for gay couples. If lawmakers approve full marriage rights, Hawaii would join 14 other states and the District of Columbia in recognizing same-sex marriage.
In calling the special session, Governor Neil Abercrombie said legalizing gay marriage would help resolve a pending federal lawsuit and also put Hawaii in line with Supreme Court rulings, which don’t apply to couples in civil unions.
Proponents say granting equality would exemplify the state’s aloha spirit — the word literally means “love’’ in Hawaiian — and also spur tourism.
Some opponents of the proposed law contend that marriage should be between a man and a woman.
Others say the matter should have a regular vote, not be rushed outside the legislative calendar.
For Dr. Allan Wang, a 56-year-old Hawaii doctor, the issue is about being treated fairly.
‘‘It’s unfair that our amazing relationship — which we’ve been together over 33 years — our amazing relationship cannot be acknowledged,’’ Wang said, sitting next to his partner, Tom Humphreys, a longtime molecular biology professor at the University of Hawaii at Manoa.
Wang and Humphreys, 77, married in California in July, one month after entering a civil union in Hawaii and after decades of pressing for gay marriage in the state. Humphreys said they were effectively forced to marry outside Hawaii after he was diagnosed with terminal prostate cancer and told he had only a short time to live.
They married exactly one week after the Supreme Court struck down the Defense of Marriage Act, granting federal benefits to legally married gay couples. Congress had passed the act as part of a growing backlash to a case from Hawaii, after a couple tried to apply for a marriage license in 1990.
Differences between civil unions and full-fledged marriage have been a key part of the debate in Hawaii. A lawsuit pending in the Ninth US Circuit Court of Appeals argues that gay couples should be allowed to marry and shouldn’t have to settle for civil unions.
On Friday, Attorney General Martha Coakley of Massachusetts filed a brief in the federal appeals case and another case from Nevada involving couples who maintain that the state’s ban violates the 14th Amendment to the US Constitution. Attorneys general from 14 other states are listed as co-counsel in the brief.
Hawaii and Nevada provide many protections for same-sex couples, but deny them full marriage status.
Coakley said the experience in Massachusetts, the first state to legalize gay marriage, shows that allowing same-sex couples to marry only strengthens the institution of marriage.
Coakley led the filing of the amicus brief on behalf of Massachusetts, California, Connecticut, Delaware, Iowa, Illinois, Maine, Maryland, New Hampshire, New Mexico, New York, Oregon, Vermont, Washington and the District of Columbia.
Lawmakers and followers of Hawaii’s Legislature — which is heavily Democratic — say they are confident a bill will pass, but not certain.
Representative Chris Lee, a Kailua Democrat who supports the bill, said legislators have been bombarded by passionate calls on both sides.
Jim Hochberg, president of Hawaii Family Advocates, said coalitions from every Hawaii island are building to push for a public vote.
‘‘They don’t support the concept of same-sex marriage. They don’t support the special session,’’ Hochberg said. ‘‘They want to vote on it.’’
The legislative hearings are expected to draw heavy crowds, with an opposition rally planned Monday night.
In Oklahoma next week, Darren Black Bear, 45, and his partner of nine years, Jason Pickel, 36, plan to be legally married, even though the state bans same-sex marriage. Their marriage license is being granted by the Cheyenne Arapaho Tribe, which is among the few Native American tribes in the United States that allow same-sex marriage.
Like all federally recognized tribes, the Cheyenne Arapaho can approve laws for its land and members.
Its code regarding marriage doesn’t address gender, referring to the parties simply as ‘‘Indians,’’ and requires that one person be a member of the tribe and reside within its jurisdiction.
Like gay couples who legally marry in other states, Black Bear and Pickel will not be awarded state benefits given to married couples in Oklahoma. But they will receive federal marriage benefits, including health insurance.
At least six other tribes allow same-sex marriage, including the Coquille Tribe in Oregon and the Little Traverse Bay Bands of Odawa Indians in Michigan, states that also ban same-sex marriage, according to national gay marriage advocacy group Freedom to Marry. Other tribes, such as the Cherokee Nation, specifically bar gay marriage.