FACTBOX: U.S. laws on gay marriage, civil unions

(Reuters) - Maine’s citizenry voted on Tuesday to repeal a law permitting same-sex marriage that was approved by state lawmakers and signed by the state’s governor in May.

Maine’s law, which had been due to take effect in September, garnered enough support from opponents to appear on Tuesday’s ballot as a “people’s veto.”

Following is a look at laws on gay marriage and same-sex civil unions in the United States.

* Maine’s reversal knocks back down to five the number of U.S. states that have currently approve gay marriage: Iowa, Connecticut, Massachusetts, New Hampshire and Vermont.

* Forty U.S. states have laws explicitly prohibiting such marriages, including 29 with constitutional amendments restricting marriage to one man and one woman, according to the Human Rights Campaign, a gay rights advocacy group.

* The first legal same-sex marriages in the United States took place in Massachusetts in 2004, a year after the state’s highest court ruled that a ban on gay marriage was unconstitutional. On July 8, Massachusetts sued the U.S. government to seek federal marriage benefits for same-sex couples in a move challenging the constitutionality of the federal 1996 Defense of Marriage Act. About 16,000 gay and lesbian couples have married in the state since 2004.

* California’s Supreme Court backed a ban on gay marriage on May 26, 2009, upholding a voter-approved proposition defining marriage as between a man and a woman, but saying the marriages last year of 18,000 same-sex couples were still legal. Ted Olson and David Boies, the lawyers who faced off in the 2000 U.S. presidential election vote recount, filed a federal lawsuit aimed at the Supreme Court arguing that a gay marriage ban is unconstitutional. A full trial is scheduled for January. In September, gay right activists submitted a ballot proposal for the November 2010 election in hopes of winning back the right to wed in California. In October, Governor Arnold Schwarzenegger signed a bill that recognizes same-sex marriages performed in other states. The law goes into effect on January 1.

* Connecticut legalized gay marriage in October 2008, when its Supreme Court overturned a ban on same-sex marriage. Local authorities began issuing marriage licenses in November.

* Iowa’s supreme court issued a unanimous ruling on April 3 that said a gay marriage ban violated the constitutional rights of gay and lesbian couples. The state’s first legal same-sex weddings took place later that month.

* On April 7, Vermont lawmakers overrode a governor’s veto of a gay-marriage bill, making the New England state the first in the country to legalize gay marriage with a legislative vote. Its law took effect on September 1.

* The District of Columbia city council voted on May 5 to recognize same-sex marriages performed in states where those unions are legal, although gay marriages cannot be conducted in the city itself.

* The New York State Assembly passed a bill on May 12 to legalize gay marriage, but it faces an uncertain future in the state Senate, where a leadership struggle has deadlocked the body.

* New Hampshire on June 3 authorized gay marriage after its Democratic-controlled House of Representatives endorsed the move, hours after the state Senate approved the legislation along party lines. Governor John Lynch, a Democrat, signed the bill, which goes into effect on January 1.

* New Jersey permits same-sex civil unions that grant largely the same state rights as those afforded married couples -- from insurance coverage to tax benefits and hospital visiting rights -- but lack the full legal protections of marriage.

* Hawaii, California, Oregon and Washington offer gay couples some legal rights as partners.

* The patchwork of laws has caused some unusual complications. Rhode Island’s top court, for example, ruled in December 2007 that a same-sex couple married in Massachusetts could not legally divorce in Rhode Island, saying the state’s family court did not have authority over same-sex marriage. In Texas, on the other hand, a judge ruled in October that the state’s gay marriage ban is unconstitutional and that two men married in another state can divorce in Texas.

* The U.S. Supreme Court has not taken a case on gay marriage, leaving states to decide on the issue, although the California federal challenge is aimed at eventually reaching the country’s top court.

Compiled by Ros Krasny in Boston, Edith Honan in New York, Courtney Hoffman in San Francisco; editing by Anthony Boadle