France's top court refused Wednesday to allow French citizenship for 10-year-old twin girls born to a surrogate mother in the United States, in a ruling that affirmed France's legal ban on surrogacy.

In a case straddling international legal rights and bioethics, the Court of Cassation ruled a California county went too far by ruling that a French couple are legally the twins' parents.

The ruling exposes the legal limbo that many would-be parents find themselves in because of inconsistencies on surrogacy between countries like the United States, which legally recognizes it, and France, which does not.

Other countries, like Belgium, are largely silent on the subject, leaving the door open to different interpretations and leaving an international legal void in many cases.

Because Sylvie Mennesson was unable to bear children, she and her husband, Dominique, turned to a surrogate mother with his sperm and a donor's egg. The surrogate mother gave birth to the twins in California in 2000, and the girls have U.S. citizenship. Under California's surrogacy rights laws, San Diego County said the Mennessons were the girl's legal parents.

Wednesday's ruling follows a lower court's order that stripped the twins from France's civil registry. Being listed on the civil registry is a requirement for obtaining documents including identity cards or passports.