The Fourth District Court of Appeal on Wednesday struck down the law, which the state's lawyers had refused to defend. It was heavily criticized because it required mothers, including rape victims and underage girls, to widely publish potentially embarrassing information.
Adoption advocates said the law even encouraged abortions.
The court also said the state failed to show how the rights of the father or the state could outweigh the privacy rights of the mother and child "in not being identified in such a personal, intimate and intrusive manner."
"It subjected women to public humiliation and harassment for no benefit," said Mariann Wang, an attorney with the ACLU Reproductive Freedom Project.
The law required a mother who wanted to put her child up for adoption to take out newspaper advertisements listing her name, age and description, and the descriptions of any men who could have been the father. The ads had to run once a week for a month in any city where the child was believed to be conceived.
The goal was to find the father of babies being put up for adoption and stave off potential custody battles that can break up adoptive families.
The law prohibited anyone from opposing an adoption after two years.
When lawmakers signed off on the bill two years ago, they cited the three-year fight over Baby Emily, whose father, a convicted rapist, contested her adoption. The Florida Supreme Court ruled in 1995 that Emily's adoptive parents should keep her, but told lawmakers to set a deadline for challenging adoptions.
Six women and the American Civil Liberties Union had asked the appeals court to strike down the law, saying it was holding up many of the 5,000 to 7,000 adoptions conducted in Florida every year.
"A lot of women's lives and children's lives have been on hold for all this time so it's a wonderful thing that women's rights have finally been vindicated and protected," Wang said.
Democratic state Sen. Walter Campbell, who sponsored the bill, has said the law had unintended consequences. He did not immediately return a call seeking comment.
Campbell is now pushing for a law that would establish a confidential registry allowing men who believe they could have fathered a child to come forward. If a woman they named as a partner puts a baby up for adoption, the man would be notified in case he wants to protect his parental rights.
Adoption advocates have backed the new proposal.
By Jill Barton