Blu-Ray discs can carry offline updates that blacklist other discs. All players must support these updates as part of licensing the technology. All your blu-rays may play today, but if an update comes along to revoke the license on a title and you play a disc that carries the update that enables that revocation, it won’t play back on your device. It’s occasionally been used to disable known pirated discs, and so far hasn’t been used on licensed materials, but “so far” is never much assurance.