SAN JOSE, Costa Rica (AP) -- Conservative Costa Rican lawmakers are getting a lesson in the importance of reading the fine print.
They were mortified on Friday after realizing that they may have accidentally approved language making same-sex unions legal when they passed a piece of legislation this week.
President Laura Chinchilla on late Thursday signed the bill governing social services and marriage regulations for young people.
The mostly conservative members of Congress didn't notice that the final version of the bill had changed earlier language that defined marriage as a union between a man and a woman.
After realizing they had approved a bill that "confers social rights and benefits of a civil union, free from discrimination," the lawmakers asked Chinchilla to veto the new law. She refused.
Conservative Congressman Justo Orozco of the Christian Costa Rican Renovation Party said he and other right-wing lawmakers will launch a legal challenge to the new law.
"That law goes against family law and the Costa Rican constitution itself," Orozco said.
The change to the bill was proposed by leftist lawmaker Jose Villalta of the Broad Front Party, who said it was passed unanimously. "The problem is that there are lawmakers who don't read what they are voting on," Villalta said.
Yashin Castrillo, a lawyer, filed an appeal after Chinchilla signed the law Thursday asking the Constitutional Court, the highest court in the Central American country, to recognize his union with his boyfriend.
Same-sex marriage is already legal in more than a dozen nations worldwide. In Latin America, gay marriage is legal in Argentina and Mexico City.
Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.