Same-sex marriage is sweeping Latin America thanks to the influence of the most revered judicial institution in the Western Hemisphere. It's a court that is unafraid to tackle the weightiest social problems or to belatedly embrace gay rights—a rarefied chamber that holds foreign courts in the highest respect and whose respect is reciprocated enthusiastically around the world. I speak, of course, not of the U.S. Supreme Court, but of the Inter-American Court of Human Rights in San Jose, Costa Rica.

In last summer's pro bono column, The Global Lawyer predicted that the Inter-American court ruling in Atala v. Chile, granting custody to a lesbian mother, would "reverberate around the world through judicial dialogue." Happily, this prediction rapidly came true in ways both literal and metaphorical.

In a bit of judicial dialogue that I did not envision, Chile's chief justice publicly apologized to the lesbian mother, Judge Karen Atala, for taking her children away. This extraordinary exchange—see here for the video—easily surpasses Kuwait's $2.195 billion payment to Dow Chemical as the most gratifying enforcement of a global dispute this year.

More importantly, courts have picked up on Atala v. Chile's proclamation that the Inter-American Convention on Human Rights forbids "any rule, act, or discriminatory practice based on sexual orientation." Now there is a principle just begging to be picked up by a lawyer who, whether through a surfeit of experience or blissful inexperience, has the temerity to ask a court to change the world.

Alex Ali Mendez Diaz was a Mexican law student with lesbian friends who wanted to get married in Oaxaca. He thought they had a valid legal argument, and like his more venerable counterparts, David Boies and Theodore Olson, he ignored the chorus of voices urging caution. Mendez cited Atala v. Chile to the Mexican Supreme Court, and in December 2012 the Mexican court accepted his argument, clearing the way for gay marriage to be legalized in every Mexican state.

As the journalist J. Lester Feder has ably documented, same-sex marriage is surging through much of Latin America. The right of gays to wed has also been promoted by legislatures in Argentina and Uruguay, and by judicial bodies in Colombia (with pushback by the legislature) and Brazil.

"The dynamics are different in every country," Feder notes, "but there is one thing that unites them: They all care a lot more about international law than the United States." Indeed, the U.S. Supreme Court sometimes manages to be insular even when it's in tune with global trends. The only mention of foreign courts in this June's landmark decisions on gay rights was a sneering reference in a dissent by Justice Antonin Scalia.

I observed in A People's History of the European Court of Human Rights that the ECHR forms a progressive parallel universe to which the U.S. has traditionally been oblivious. Perhaps the most blatant example was America's Bowers v. Hardwick, which in upholding a ban on gay sex in 1986, displayed embarrassing ignorance of Dudgeon v. United Kingdom, which had reached the opposite result on identical facts in 1981. America partly redeemed itself with Lawrence v. Texas (2003), which overturned Bowers while belatedly giving significant respect to the Dudgeon opinion. But in general, the U.S. still remains at the margins of global judicial dialogue.

Now perhaps it is the Inter-American system that is developing a progressive parallel universe. As democracy has strengthened in the region, the court in San Jose has slowly found its voice on a range of issues. Last summer's pro bono column showed how lawyers at Morrison & Foerster helped Karen Atala build a base for gay rights in the Inter-American Court. Now, Feder reports, several groups plan to expressly establish a right to gay marriage in the Inter-American Commission.

The first test case was filed by three Chilean couples with the help of pro bono lawyers from Arent Fox. With any luck, they will be featured in The Global Lawyer next summer.