In the state where I live, the penal code includes the legal definitions of words such as “theft”.
The legal system here does not use a Webster’s dictionary to define words. We use the penal code, code of criminal procedure, traffic code and other legal guidance codes to define the meanings of words used in the law and in official government communications.
These are the definitions that would be used by complainants in cases brought against pirates, if such a case were to be brought. For that reason, I believe these definitions are relevant here.