You typically sue a company over torts, not crimes. A tort is a civil cause of action. "They deprived me of my property in a fashion we had not agreed upon" i

You typically sue a company over torts, not crimes. A tort is a civil cause of action. "They deprived me of my property in a fashion we had not agreed upon" is a tort called conversion. There exist many other ones you could describe Mt. Gox as having committed. Japan and the US are friendly first-world nations; their courts routinely enforce each others' judgments. (You'd have to demonstrate tortious behavior in the US to the satisfaction of a Japanese court, which might not be straightforward, but that's the sort of thing you'd want to ask an actual Japanese lawyer rather than somebody with a cursory understanding of the matter.) That said, most people hoping for recourse in a court of law do not understand the expense, timeline, and likelihood of actual collection involved. (Six figures, years, and "probably nil", respectively.)