It is an anonymous work or pseudonymous work and 50 years have passed since the date of its publication (or creation, whatever date is the latest)
It is a collective, audiovisual or a work of applied art, and 50 years have passed since the date of its publication (or creation, whatever date is the latest)
It is a posthumous work and 50 years have passed since the date of its publication
It is another kind of work, and 50 years have passed since the year of death of the author (or last-surviving author)
It is one of "laws, court judgments and other official instruments, as well as their official translations, coats of arms, decorations, currency marks and other official insignia"