Carol Robles-Román, the president and chief executive of Legal Momentum, a women’s legal defense and education fund based in New York, said she had been lobbying for action against Backpage for two years, saying the ads it hosts were targeting children.

Backpage describes itself as the second-largest online classified advertising service in the country, according to court records.

“They’re like the McDonald’s of trafficking,” she said in an interview on Thursday night. “They made is so easy.”