MOSCOW — Russia’s children’s ombudsman vigorously endorsed the ban on U.S. adoptions Thursday, saying there was no chance it would be lifted no matter how large the protest. However, the 50 or so American families who have received court decisions will be able to take their children home, he said.

In a combative news conference, Pavel Astakhov, the ombudsman, said he has been opposed to U.S. adoptions ever since 2010, when a Tennessee woman put her 7-year-old alone on a plane bound for Moscow accompanied only by a note saying she was returning him because he was violent and unstable.

“We must stop selling our children,” he said.

But he repeatedly said the families with court decrees can take their children, even though regional officials have apparently been refusing to finish the adoptions. “We are talking about 52 families,” he said, “maybe more, maybe less.”

He conceded that some of those families have been denied the final paperwork and promised to intervene personally in those cases.