The US Library of Congress has rejected a petition that would allow US iPod users to copy their movies to iPods and other devices.

iPod users had petitioned for the right to break the encryption technology on DVDs they legally own in order to rip the movies to iTunes and to their iPods.

However, the Library of Congress has loosened the rules protecting DVD encryption to allow professors of movie studies to break copy protection for educational use.

Professors had been asking for - and have now received - the right to break the copy protection on DVDs in order that they could put together compilations of movie clips for their classes.

Under US laws, they were unable to legally do this, and studios had argued that they could use VHS to do the same thing.