The Marriage Equality Act, which New York State passed in June 2011, allowed Jann Paczkowski to marry her partner, Jamie, with the assurance that “the marriages of same-sex and different-sex couples” would “be treated equally in all respects under the law.” But when the couple separated and Ms. Paczkowski sought joint custody of the 2-year-old boy they were raising together, she discovered the limits of that assurance. On June 30, 2014, a judge in Nassau County family court ruled that Ms. Paczkowski did not have legal standing to seek access to the boy — because even under the Marriage Equality Act, she was not his parent.

In his decision, Judge Edmund M. Dane acknowledged “inequity” and “imbalance” in the law, adding that if Ms. Paczkowski were a man in the same position, the law might point toward a different ruling. But in the end, he left Jann with no contact with the boy.

The decision devastated Ms. Paczkowski, 36. “You can see how angry and upset I am,” she said on a recent afternoon, seated beside her court-appointed lawyer after a morning spent moving cars for an auction house. She had not seen the boy since a brief visit on Mother’s Day.

“For 17 1/2 months I changed his diaper in the quickness of a dime,” she said. “I fed him. I sat him in a high chair, one spoonful for you, one for me. At night he crawled up to me in bed. Each step that my son took, I did it with him. That’s what a parent does.”