The estates of Mitch Mitchell and Noel Redding can go forward suing Sony over Jimi Hendrix royalties they hope to claim, despite signing off on those in the Seventies. London's High Court has ruled that the case can go forward. From the Guardian:
Aside from a tiny handful of Redding-penned songs, Hendrix wrote the group’s repertoire and earned the songwriting royalties alone, but the trio shared in royalties for the sound recordings they created together prior to Hendrix’s death aged 27 in 1970.
Believing there would not be any more Jimi Hendrix Experience music released – and with the lucrative CD-reissue and streaming eras still years in the future – the pair signed away their rights in the early 1970s. Redding received $100,000 while Mitchell received $240,000, with both signing documents that stated they would not be able to make future lawsuits over the earnings.

