That would imply you're smarter and have more power than the law which is not the case.

They'd ask you to provide actual readable files, pictures, etc, or else would reject your "decryption".

It is true but not really relevant that they're smarter and more powerful than me. Since they don't trust me, they won't let me decrypt the disk D but will demand the key K to do it themselves. Recall K = D XOR P for some readable plaintext pictures or files, etc., I've already chosen. The "decryption" yields the perfectly readable output P = D XOR K.

Well, I read the original comment as being a: "here, K is the password, D XOR K is your results" idea -- based on that any D XOR K is technically a decryption, whether random stuff comes from the process.

If you intend K to provide "perfectly readable output", then

(1) if you actually produced the contents of D yourself to hide data, then you need to come up with some scheme so that K provides "perfectly readable output" and some alternative V provides D XOR V (or another decryption scheme) that gives you your actual secrets. I don't think it's that easy to have "perfectly readable data" on D XOR K plus have your secrets with another key. Except if you mean through steganography, but then K is not needed at all.

(2) if you were just send a random noise drive to "frame you" then you need access to the drive to come up with a K so that D XOR K decrypts to valid data.

This is a one-time pad. Given a ciphertext D it's trivial to come up with a key K that "decrypts" D to whatever plaintext P you want (K = D XOR P). This is why one-time pads are immune to brute-force search.