.. or, there is a law, but immigrants aren't following it.

http://www.dw.com/en/german-cabinet-proposes-national-ban-on-child-marriages/a-38306852

"German Chancellor Angela Merkel's government has agreed on a new draft law aimed at outlawing child marriages. By the end of July 2016, almost 1,500 minors with non-German backgrounds were registered there as married."

"According to the Cologne-based Central Register of Foreign Nationals (AZR), by the end of July 2016, almost 1,500 minors with non-German backgrounds living in the country were registered as married - 361 of them aged under 14."

(excuse the misspelling of marriage in title, I can't seem to edit it.)