Last year, Willis invoked a part of US copyright law called 'termination rights' - which, according to the NY Times, gives recording artists and songwriters the ability to reacquire and administer their work themselves after 35 years have elapsed.

The two companies that administer publishing rights to the group's songs, Scorpio Music and Can't Stop Productions, fought a court case seeking to ensure that Willis couldn't regain control over the song rights.

The song publishers, Scorpio Music and Can't Stop ...