Starting Thursday, gay marriage is legal in Mexico City.

Lawmakers approved the law that gives gay couples all the rights and responsibilities of marriage, including the right to adopt children, in December. Previously, the city government recognized gay couples with civil unions, but gay adoption was banned.

The law is a first for Latin America. However, the first gay wedding took place late last year in Argentina. Alejandro Freyre, 39, and Jose Maria Di Bello, 41, were married in the state of Tierra del Fuego after its governor issued a special decree, but gay marriage is not legal in the country. Uruguay remains the only Latin American country to recognize gay couples, who can apply for a civil union.

There is little chance of exporting gay marriage to other parts of the country, which is largely controlled by the conservative PAN Party. Mariana Gozmez del Campo, who heads the PAN in Mexico City, said lawmakers violated the rights of minors by allowing gay couples to adopt.

In an effort to derail the start of the law, Mexico's federal government appealed to the country's Supreme Court. The federal Attorney General's Office argued that the law was unconstitutional because it “strays from the responsibility of the government to place a priority on safeguarding the interests of children.”

While the court has yet to review the federal challenge, it upheld the law in rejecting challenges brought by the governors of three states controlled by the PAN Party. The governors had argued that the law would force their state governments to recognize the marriages of gay couples from Mexico City. The court, however, said the states did not have the legal authority to challenge the laws of another state or the nation's federal district of Mexico City.

Residents of Mexico's largest city – approximately 10 million – have mixed feelings on the law. A recent survey by the pollster BGC-Ulises Beltran found supporters outnumbered opponents by a narrow 3% (46% vs. 43%).

Less ambiguous is the Roman Catholic Church, which has condemned the law, especially its provision legalizing gay adoption. Mexico's Catholic archbishop, Cardinal Noberto Rivera Carrera, has called the law “immoral” and “reprehensible.”

Gay couples can apply for a marriage license starting on Thursday, but processing could take up to 10 days, making next week the earliest gay couples could tie the knot.