In New York and 11 other states, if a mother is accused of abuse or neglect but the father is not, and he is not married to her, he must prove that he is a parent in his own right — otherwise he will not have a say in whether the child is put up for adoption. In most of those states, including New York, proof means paying child support — not to the mother but to the government agency that has taken the child.

“This is just blatant discrimination based on stale gender stereotypes — that the only way to be a father is to have a wedding ceremony or else to be a kind of rote financial provider,” said Martin Guggenheim, a law professor at New York University who studies family law and children’s rights.

Defenders of the New York law, which dates to 1980, say it helps children who have been languishing in foster care to get a permanent home sooner by preventing unmarried fathers who do not support their children from using the courts to delay or stop an adoption.

If those fathers had full rights, “we would have to prove by clear and convincing evidence that he abandoned the child … which can take years,” said Ira L. Eras, a New York lawyer who has mostly represented foster care agencies for three decades.

A F amily Court judge in Manhattan ended Ping’s parental rights last year, paving the way for Amanda’s adoption by another family. The judge cited Ping’s status as an unwed father at the time of his daughter’s birth and his failure to pay child support to Catholic Guardian Services, the foster care agency that the city’s child welfare arm, the Administration for Children’s Services, had hired to take custody of the girl.