PORTLAND – The lawyer who wrote the legal briefs that convinced the highest court in Massachusetts to allow gay marriages is no stranger to Maine.

Mary Bonauto, the lead civil rights lawyer for the Boston-based Gay & Lesbian Advocates & Defenders, launched her legal career in Maine and lives in Portland with her partner and their twin daughters.

Bonauto, 42, wrote the briefs in Portland and is well-known to Mainers involved in the struggle for equal rights for lesbian and gay people.

Bonauto has represented people with AIDS who were denied medical treatment. She provided the legal analysis for all of Maine’s referendum campaigns seeking to establish the civil rights of gay and lesbian men and women.

Earlier this month, Bonauto won a ruling from Maine’s highest court, which could make it easier for same-sex couples to have full legal status as parents.

“There isn’t a single significant piece of litigation in the area of gay and lesbian civil rights that Mary Bonauto has not been involved in, and that is true through most of New England,” said Patricia Peard, a Portland lawyer who has worked with Bonauto for over a decade. “She is one of the pre-eminent civil rights attorneys in the nation.”

Tuesday’s ruling by the Massachusetts Supreme Judicial Court puts Bonauto at the center of a national debate on same-sex marriage.

“We get over 3,000 calls a year at GLAD,” Bonauto said in a telephone interview Wednesday from her Boston office. “If there was [same-sex] marriage, half of those problems would go away.”

In her briefs and argument before the Massachusetts court, Bonauto stressed the difference between the marriage covenant created by religion and the legal relationship of civil marriage, through which the government grants benefits to some citizens and not others.

“There is nothing like marriage,” she said. “It’s really a case where you don’t have complete equality and fairness under the law.”

A native of Newburgh, N.Y., and a graduate of Hamilton College and Northeastern University School of Law, Bonauto moved to Portland in 1989 for her first job as an associate for MittelAsen LLC.

When Massachusetts passed the nation’s first gay and lesbian civil rights law, Bonauto left Maine to take a new job at GLAD. But her work brought her back here often.