On March 15, Japan's Supreme Court issued an important decision in a case arising under the Hague Convention on child abduction. Except it wasn't about the convention, but about habeas corpus. Most press accounts have characterized the ruling as ordering that a child brought to Japan by his mother be returned to the United States, but it's a bit more complicated.

A pitfall of comparative law is the ease with which familiar-sounding terminology can mislead. "Habeas corpus" is a prime example.

Latin for "produce the body," habeas corpus is a centuries-old judicial procedure that in the Anglo-American system formed the bedrock of human rights law before the concept of human rights existed. A person subjected to arbitrary, unlawful detention could petition a court to issue a writ of habeas corpus. If the writ was issued, the detainer had to bring the detainee to court and explain the grounds for detention. If the detention was found to be unlawful, the detainee was immediately set free.