Now there are of course tools to play blu-rays and related media on PCs (e.g. something like Cyberlink's PowerDVD) so they need to have some means to get authorized access to the protected media and thus the keys must be hard-coded into the program and if they are not hard-coded, at least an oracle access to the GPU's hardware-protected keys must be hard-coded.
So my question is simple:
What prevents an attacker from reverse engineering the player software and using the (valid) keys or the oracle access to make illegal (high-quality) media copies?
As usual, I don't want to hear about "it's against the software license" as answer, because this may prove ineffective in (quite) some situations. In other words: I'd like to hear the technical defenses used in DRM.
Please note further: This is a theoretical question and I do not plan on actually applying any knowledge learned by this question for unlawful purposes, the answers may be restricted (at the discretion of the author) to not be directly usable as attacks without major efforts. Furthermore I would prefer to only have public documents as sources here.