system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars ROTJ] When Luke asks Vader to leave the Empire and follow him, Vader says "You don't know the power of the dark side, I MUST obey my master". Is Vader making a statement or warning Luke that that he cannot do anything regarding the matter?

It almost sounds like Vader would love to leave the Emperor, but cannot because he's too powerful to be disobey and incur the consequence. Is he simply telling Luke that his hands are tied regarding the matter and that he cannot leave Palpatine?

Basically, who's talking here, Anakin or Vader?
gpt
I read it as Anakin talking, but not exactly in the way you mention.  It's not that Anakin wants to leave, but fears Palpatine's power.  There is a component of that, but that's not the main thing.

He didn't say "you don't know his power".  It's the "power of the Dark Side" that's the main driver here.  

It's addictive, and Anakin is speaking as an addict here.  He's expressing that desire to return to the light, but knows that in so doing he will lose that seductive power, and thus must obey his master in order to preserve the ability to feed his addiction, even though he knows that's wrong.   

Which is why Vader is offering to overthrow the Emperor and lead the galaxy as father and son.  That's his path to being free of Palpatine without giving up his addiction to the Dark side power.